diff --git a/depends/Makefile b/depends/Makefile
index bdaa666b5..579897c9a 100644
--- a/depends/Makefile
+++ b/depends/Makefile
@@ -1,204 +1,228 @@
 .NOTPARALLEL :
 
 # Pattern rule to print variables, e.g. make print-build_arch
 print-%:
 	@echo $* = $($*)
 
+# When invoking a sub-make, keep only the command line variable definitions
+# matching the pattern in the filter function.
+#
+# e.g. invoking:
+#   $ make A=1 C=1 print-MAKEOVERRIDES print-MAKEFLAGS
+#
+# with the following in the Makefile:
+#   MAKEOVERRIDES := $(filter A=% B=%,$(MAKEOVERRIDES))
+#
+# will print:
+#   MAKEOVERRIDES = A=1
+#   MAKEFLAGS = -- A=1
+#
+# this is because as the GNU make manual says:
+#   The command line variable definitions really appear in the variable
+#   MAKEOVERRIDES, and MAKEFLAGS contains a reference to this variable.
+#
+# and since the GNU make manual also says:
+#   variables defined on the command line are passed to the sub-make through
+#   MAKEFLAGS
+#
+# this means that sub-makes will be invoked as if:
+#   $(MAKE) A=1 blah blah
+MAKEOVERRIDES := $(filter V=%,$(MAKEOVERRIDES))
 SOURCES_PATH ?= $(BASEDIR)/sources
 WORK_PATH = $(BASEDIR)/work
 BASE_CACHE ?= $(BASEDIR)/built
 SDK_PATH ?= $(BASEDIR)/SDKs
 NO_QT ?=
 NO_PROTOBUF ?=
 NO_QR ?=
 NO_WALLET ?=
 NO_ZMQ ?=
 NO_UPNP ?=
 NO_JEMALLOC ?=
 FALLBACK_DOWNLOAD_PATH ?= https://download.bitcoinabc.org/depends-sources
 
 BUILD = $(shell ./config.guess)
 HOST ?= $(BUILD)
 PATCHES_PATH = $(BASEDIR)/patches
 BASEDIR = $(CURDIR)
 HASH_LENGTH:=11
 DOWNLOAD_CONNECT_TIMEOUT:=30
 DOWNLOAD_RETRIES:=3
 HOST_ID_SALT ?= salt
 BUILD_ID_SALT ?= salt
 JOBS ?= $(shell echo $$(($(shell nproc 2> /dev/null || sysctl -n hw.ncpu 2> /dev/null || echo 0) + 1)))
 
 host:=$(BUILD)
 ifneq ($(HOST),)
 host:=$(HOST)
 host_toolchain:=$(HOST)-
 endif
 
 ifneq ($(DEBUG),)
 release_type=debug
 else
 release_type=release
 endif
 
 base_build_dir=$(WORK_PATH)/build
 base_staging_dir=$(WORK_PATH)/staging
 base_download_dir=$(WORK_PATH)/download
 canonical_host:=$(shell ./config.sub $(HOST))
 build:=$(shell ./config.sub $(BUILD))
 
 build_arch =$(firstword $(subst -, ,$(build)))
 build_vendor=$(word 2,$(subst -, ,$(build)))
 full_build_os:=$(subst $(build_arch)-$(build_vendor)-,,$(build))
 build_os:=$(findstring linux,$(full_build_os))
 build_os+=$(findstring darwin,$(full_build_os))
 build_os:=$(strip $(build_os))
 ifeq ($(build_os),)
 build_os=$(full_build_os)
 endif
 
 host_arch=$(firstword $(subst -, ,$(canonical_host)))
 host_vendor=$(word 2,$(subst -, ,$(canonical_host)))
 full_host_os:=$(subst $(host_arch)-$(host_vendor)-,,$(canonical_host))
 host_os:=$(findstring linux,$(full_host_os))
 host_os+=$(findstring darwin,$(full_host_os))
 host_os+=$(findstring mingw32,$(full_host_os))
 host_os:=$(strip $(host_os))
 ifeq ($(host_os),)
 host_os=$(full_host_os)
 endif
 
 $(host_arch)_$(host_os)_prefix=$(BASEDIR)/$(host)
 $(host_arch)_$(host_os)_host=$(host)
 host_prefix=$($(host_arch)_$(host_os)_prefix)
 build_prefix=$(host_prefix)/native
 build_host=$(build)
 
 AT_$(V):=
 AT_:=@
 AT:=$(AT_$(V))
 
 all: install
 
 include hosts/$(host_os).mk
 include hosts/default.mk
 include builders/$(build_os).mk
 include builders/default.mk
 include packages/packages.mk
 
 build_id_string:=$(BUILD_ID_SALT)
 build_id_string+=$(shell $(build_CC) --version 2>/dev/null)
 build_id_string+=$(shell $(build_AR) --version 2>/dev/null)
 build_id_string+=$(shell $(build_CXX) --version 2>/dev/null)
 build_id_string+=$(shell $(build_RANLIB) --version 2>/dev/null)
 build_id_string+=$(shell $(build_STRIP) --version 2>/dev/null)
 
 $(host_arch)_$(host_os)_id_string:=$(HOST_ID_SALT)
 $(host_arch)_$(host_os)_id_string+=$(shell $(host_CC) --version 2>/dev/null)
 $(host_arch)_$(host_os)_id_string+=$(shell $(host_AR) --version 2>/dev/null)
 $(host_arch)_$(host_os)_id_string+=$(shell $(host_CXX) --version 2>/dev/null)
 $(host_arch)_$(host_os)_id_string+=$(shell $(host_RANLIB) --version 2>/dev/null)
 $(host_arch)_$(host_os)_id_string+=$(shell $(host_STRIP) --version 2>/dev/null)
 
 qrencode_packages_$(NO_QR) = $(qrencode_packages)
 
 qt_packages_$(NO_QT) = $(qt_packages) $(qt_$(host_os)_packages) $(qt_$(host_arch)_$(host_os)_packages) $(qrencode_packages_)
 
 wallet_packages_$(NO_WALLET) = $(wallet_packages)
 upnp_packages_$(NO_UPNP) = $(upnp_packages)
 zmq_packages_$(NO_ZMQ) = $(zmq_packages)
 
 protobuf_packages_$(NO_PROTOBUF) = $(protobuf_packages)
 
 jemalloc_packages_$(NO_JEMALLOC) = $(jemalloc_packages)
 
 packages += $($(host_arch)_$(host_os)_packages) $($(host_os)_packages) $(qt_packages_) $(wallet_packages_) $(upnp_packages_)
 native_packages += $($(host_arch)_$(host_os)_native_packages) $($(host_os)_native_packages)
 
 ifneq ($(protobuf_packages_),)
 native_packages += $(protobuf_native_packages)
 packages += $(protobuf_packages)
 endif
 
 ifneq ($(zmq_packages_),)
 packages += $(zmq_packages)
 endif
 
 ifneq ($(jemalloc_packages_),)
 packages += $(jemalloc_packages)
 endif
 
 all_packages = $(packages) $(native_packages)
 
 meta_depends = Makefile funcs.mk builders/default.mk hosts/default.mk hosts/$(host_os).mk builders/$(build_os).mk
 
 $(host_arch)_$(host_os)_native_toolchain?=$($(host_os)_native_toolchain)
 
 include funcs.mk
 
 final_build_id_long+=$(shell $(build_SHA256SUM) config.sub)
 final_build_id+=$(shell echo -n "$(final_build_id_long)" | $(build_SHA256SUM) | cut -c-$(HASH_LENGTH))
 $(host_prefix)/.stamp_$(final_build_id): $(native_packages) $(packages)
 	$(AT)rm -rf $(@D)
 	$(AT)mkdir -p $(@D)
 	$(AT)echo copying packages: $^
 	$(AT)echo to: $(@D)
 	$(AT)cd $(@D); $(foreach package,$^, tar xf $($(package)_cached); )
 	$(AT)touch $@
 
 define check_or_remove_cached
   mkdir -p $(BASE_CACHE)/$(host)/$(package) && cd $(BASE_CACHE)/$(host)/$(package); \
   $(build_SHA256SUM) -c $($(package)_cached_checksum) >/dev/null 2>/dev/null || \
   ( rm -f $($(package)_cached_checksum); \
     if test -f "$($(package)_cached)"; then echo "Checksum mismatch for $(package). Forcing rebuild.."; rm -f $($(package)_cached_checksum) $($(package)_cached); fi )
 endef
 
 define check_or_remove_sources
   mkdir -p $($(package)_source_dir); cd $($(package)_source_dir); \
   test -f $($(package)_fetched) && ( $(build_SHA256SUM) -c $($(package)_fetched) >/dev/null 2>/dev/null || \
     ( echo "Checksum missing or mismatched for $(package) source. Forcing re-download."; \
       rm -f $($(package)_all_sources) $($(1)_fetched))) || true
 endef
 
 check-packages:
 	@$(foreach package,$(all_packages),$(call check_or_remove_cached,$(package));)
 check-sources:
 	@$(foreach package,$(all_packages),$(call check_or_remove_sources,$(package));)
 
 check-packages: check-sources
 
 clean-all: clean
 	@rm -rf $(SOURCES_PATH) x86_64* i686* arm* aarch64*
 
 clean:
 	@rm -rf $(WORK_PATH) $(BASE_CACHE) $(BUILD)
 
 install: check-packages $(host_prefix)/.stamp_$(final_build_id)
 
 download-one: check-sources $(all_sources)
 
 download-osx:
 	@$(MAKE) -s HOST=x86_64-apple-darwin16 download-one
 download-linux:
 	@$(MAKE) -s HOST=x86_64-unknown-linux-gnu download-one
 download-win:
 	@$(MAKE) -s HOST=x86_64-w64-mingw32 download-one
 download: download-osx download-linux download-win
 
 build-linux64: download-linux
 	@$(MAKE) -s HOST=x86_64-linux-gnu install
 build-linux32: download-linux
 	@$(MAKE) -s HOST=i686-pc-linux-gnu install
 build-linux-arm: download-linux
 	@$(MAKE) -s HOST=arm-linux-gnueabihf install
 build-linux-aarch64: download-linux
 	@$(MAKE) -s HOST=aarch64-linux-gnu install
 build-osx: download-osx
 	@$(MAKE) -s HOST=x86_64-apple-darwin16 install
 build-win64: download-win
 	@$(MAKE) -s HOST=x86_64-w64-mingw32 install
 
 build-all: build-linux64 build-linux32 build-linux-arm build-linux-aarch64 build-osx build-win64
 
 $(foreach package,$(all_packages),$(eval $(call ext_add_stages,$(package))))
 
 .PHONY: install cached clean clean-all download-one download-osx download-linux download-win download check-packages check-sources
diff --git a/depends/hosts/default.mk b/depends/hosts/default.mk
index 6f60d6b3f..8f9168b76 100644
--- a/depends/hosts/default.mk
+++ b/depends/hosts/default.mk
@@ -1,26 +1,35 @@
 default_host_CC = $(host_toolchain)gcc
 default_host_CXX = $(host_toolchain)g++
 default_host_AR = $(host_toolchain)ar
 default_host_RANLIB = $(host_toolchain)ranlib
 default_host_STRIP = $(host_toolchain)strip
 default_host_LIBTOOL = $(host_toolchain)libtool
 default_host_INSTALL_NAME_TOOL = $(host_toolchain)install_name_tool
 default_host_OTOOL = $(host_toolchain)otool
 default_host_NM = $(host_toolchain)nm
 
 define add_host_tool_func
+ifneq ($(filter $(origin $1),undefined default),)
+# Do not consider the well-known var $1 if it is undefined or is taking a value
+# that is predefined by "make" (e.g. the make variable "CC" has a predefined
+# value of "cc")
 $(host_os)_$1?=$$(default_host_$1)
 $(host_arch)_$(host_os)_$1?=$$($(host_os)_$1)
 $(host_arch)_$(host_os)_$(release_type)_$1?=$$($(host_os)_$1)
+else
+$(host_os)_$1=$(or $($1),$($(host_os)_$1),$(default_host_$1))
+$(host_arch)_$(host_os)_$1=$(or $($1),$($(host_arch)_$(host_os)_$1),$$($(host_os)_$1))
+$(host_arch)_$(host_os)_$(release_type)_$1=$(or $($1),$($(host_arch)_$(host_os)_$(release_type)_$1),$$($(host_os)_$1))
+endif
 host_$1=$$($(host_arch)_$(host_os)_$1)
 endef
 
 define add_host_flags_func
 $(host_arch)_$(host_os)_$1 += $($(host_os)_$1)
 $(host_arch)_$(host_os)_$(release_type)_$1 += $($(host_os)_$(release_type)_$1)
 host_$1 = $$($(host_arch)_$(host_os)_$1)
 host_$(release_type)_$1 = $$($(host_arch)_$(host_os)_$(release_type)_$1)
 endef
 
 $(foreach tool,CC CXX AR RANLIB STRIP NM LIBTOOL OTOOL INSTALL_NAME_TOOL,$(eval $(call add_host_tool_func,$(tool))))
 $(foreach flags,CFLAGS CXXFLAGS CPPFLAGS LDFLAGS, $(eval $(call add_host_flags_func,$(flags))))
diff --git a/depends/packages/boost.mk b/depends/packages/boost.mk
index c6751df08..834ba1da2 100644
--- a/depends/packages/boost.mk
+++ b/depends/packages/boost.mk
@@ -1,40 +1,43 @@
 package=boost
 $(package)_version=1_70_0
 $(package)_download_path=https://dl.bintray.com/boostorg/release/1.70.0/source/
 $(package)_file_name=$(package)_$($(package)_version).tar.bz2
 $(package)_sha256_hash=430ae8354789de4fd19ee52f3b1f739e1fba576f0aded0897c3c2bc00fb38778
 
 define $(package)_set_vars
 $(package)_config_opts_release=variant=release
 $(package)_config_opts_debug=variant=debug
 $(package)_config_opts=--layout=tagged --build-type=complete --user-config=user-config.jam
 $(package)_config_opts+=threading=multi link=static -sNO_BZIP2=1 -sNO_ZLIB=1
-$(package)_config_opts_linux=threadapi=pthread runtime-link=shared
-$(package)_config_opts_darwin=--toolset=clang-darwin runtime-link=shared
-$(package)_config_opts_mingw32=binary-format=pe target-os=windows threadapi=win32 runtime-link=static
+$(package)_config_opts_linux=target-os=linux threadapi=pthread runtime-link=shared
+$(package)_config_opts_darwin=target-os=darwin runtime-link=shared
+$(package)_config_opts_mingw32=target-os=windows binary-format=pe threadapi=win32 runtime-link=static
 $(package)_config_opts_x86_64_mingw32=address-model=64
 $(package)_config_opts_i686_mingw32=address-model=32
 $(package)_config_opts_i686_linux=address-model=32 architecture=x86
 $(package)_toolset_$(host_os)=gcc
+$(package)_toolset_darwin=clang
+ifneq (,$(findstring clang,$($(package)_cxx)))
+   $(package)_toolset_$(host_os)=clang
+endif
 $(package)_archiver_$(host_os)=$($(package)_ar)
-$(package)_toolset_darwin=clang-darwin
 $(package)_config_libraries=atomic,date_time,filesystem,system,thread,test
 $(package)_cxxflags=-std=c++11 -fvisibility=hidden
 $(package)_cxxflags_linux=-fPIC
 endef
 
 define $(package)_preprocess_cmds
   echo "using $($(package)_toolset_$(host_os)) : : $($(package)_cxx) : <cxxflags>\"$($(package)_cxxflags) $($(package)_cppflags)\" <linkflags>\"$($(package)_ldflags)\" <archiver>\"$($(package)_archiver_$(host_os))\" <striper>\"$(host_STRIP)\"  <ranlib>\"$(host_RANLIB)\" <rc>\"$(host_WINDRES)\" : ;" > user-config.jam
 endef
 
 define $(package)_config_cmds
-  ./bootstrap.sh --without-icu --with-libraries=$($(package)_config_libraries)
+  ./bootstrap.sh --without-icu --with-libraries=$($(package)_config_libraries) --with-toolset=$($(package)_toolset_$(host_os))
 endef
 
 define $(package)_build_cmds
-  ./b2 -d2 -j$(JOBS) -d1 --prefix=$($(package)_staging_prefix_dir) $($(package)_config_opts) stage
+  ./b2 -d2 -j$(JOBS) -d1 --prefix=$($(package)_staging_prefix_dir) $($(package)_config_opts) toolset=$($(package)_toolset_$(host_os)) stage
 endef
 
 define $(package)_stage_cmds
-  ./b2 -d0 -j4 --prefix=$($(package)_staging_prefix_dir) $($(package)_config_opts) install
+  ./b2 -d0 -j4 --prefix=$($(package)_staging_prefix_dir) $($(package)_config_opts) toolset=$($(package)_toolset_$(host_os)) install
 endef