This change allows macOS developers to use
WITH_COMPILER_ASAN with every generator.
CMAKE_C_IMPLICIT_LINK_DIRECTORIES on macOS points to
Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk/usr/lib
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. [1]
If users have ASAN_OPTIONS=detect_leaks=1 in their environment
variables, it should be removed to avoid a feature-unsupported error
while compiling.