[CMAKE] Add the check-symbols target

Summary:
This target runs the symbol-check.py scripts on the executables.
This is the equivalent of the autotools check-symbols rule.

Test Plan:
Build the depends subsystem for linux 64, then:

mkdir buildcmake && cd buildcmake
cmake -GNinja .. \
  -DENABLE_GLIBC_BACK_COMPAT=ON \
  -DENABLE_STATIC_LIBSTDCXX=ON \
  -DENABLE_REDUCE_EXPORTS=ON \
  -DCMAKE_TOOLCHAIN_FILE=../cmake/platforms/Linux64.cmake
ninja check-symbols

If should be successful.

Reviewers: #bitcoin_abc, deadalnix, jasonbcox

Reviewed By: #bitcoin_abc, jasonbcox

Subscribers: jasonbcox

Differential Revision: https://reviews.bitcoinabc.org/D4136