build: make building protobuf optional in depends

Summary:
Backport of core PR16871.

The logic is reversed wrt core since we enable bip70 by default.

Depends on D5637.

Test Plan:

make build-osx NO_PROTOBUF=1

Check that protobuf is not built.

../configure --prefix=$PWD/../depends/x86_64-apple-darwin16

Check in the summary that bip70 is disabled:

with bip70  = no

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D5640