Add `-Wall` compiler flag to Clang compilers.
Add `-Wall` compiler flag to Clang compilers.

Use CMAKE's `CMAKE_<LANG>_COMPILER_ID`, available from 3.0.2.
See: https://cmake.org/cmake/help/latest/variable/CMAKE_LANG_COMPILER_ID.html

taglib/taglib,taglib/taglib,taglib/taglib