This change allows macOS developers to use
WITH_COMPILER_ASAN with every generator.
CMAKE_C_IMPLICIT_LINK_DIRECTORIES on macOS points to
which is not where the Sanitizer libraries are.
To link the library, rpath could be used but that seems complex,
so linker flags are passed as the documentation says. 
If users have ASAN_OPTIONS=detect_leaks=1 in their environment
variables, it should be removed to avoid a feature-unsupported error