[build] correctly set -fstack-reuse=none only for gcc
Summary:
currently this will add the -fstack-reuse=none flag to all builds with
all compilers except those who set ENABLE_CLANG_TIDY=ON even though only
gcc knows about it
this only adds -fstack-reuse=none to gcc builds
Test Plan:
cmake -GNinja ninja -vn | grep fstack-reuse
see correct ninja dry-run with option set for gcc (it is the default compiler on my box)
cmake -GNinja -DCMAKE_CXX_COMPILER=clang++ ninja -vn | grep fstack-reuse
see no lines
Reviewers: #bitcoin_abc, deadalnix
Reviewed By: #bitcoin_abc, deadalnix
Differential Revision: https://reviews.bitcoinabc.org/D7428