[CMAKE] Improve link flag compiler support detection
[CMAKE] Improve link flag compiler support detection

Summary:
The `add_linker_flag` method is able to prevent from introducing link
time errors, but not warnings. This may cause some noise with clang,
which will issue a `-Wunused-command-line-argument` warning when an
unknown linker flag is set (then ignore it).

This diff promotes the warning to error so the unused link flag will not
be set.

Test Plan:
  mkdir buildcmake_osx && cd buildcmake_osx
  cmake -GNinja .. -DCMAKE_TOOLCHAIN_FILE=../cmake/platforms/OSX.cmake
  ninja
Check the following warning disappeared with this patch:
```
clang: warning: argument unused during compilation: '-pie'
[-Wunused-command-line-argument]
```

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D3792

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