[CMAKE] Split remove_compiler_flags into C and CXX variants
[CMAKE] Split remove_compiler_flags into C and CXX variants

Summary: Keep a `remove_compiler_flags` macro that does both.

Test Plan:
  mkdir buildcmake && cd buildcmake
  cmake -GNinja .. -DCMAKE_BUILD_TYPE=RelWithDebInfo
  ninja -v
Check the `-DNDEBUG` does not appear on the compiler command lines.

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Subscribers: teamcity, schancel

Differential Revision: https://reviews.bitcoinabc.org/D2655

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