While testing for rB40dcf686f04f: Support ASan library on macOS for all generators., compiler flags got mixed up and
non-working ASan configuration was committed.
Platform file, which is included after the CMAKE_C_FLAGS_DEBUG etc.,
are set, overwrites those flags instead of appending to them. To fix this,
PLATFORM_CFLAGS is used to pass the -fsanitize=* flags to the C/C++
Tested on fresh build using both Xcode and Ninja, with & without ccache.
Also silence a clang warning for multi-config generators:
the object size sanitizer has no effect at -O0, but is explicitly
enabled: -fsanitize=object-size [-Winvalid-command-line-argument]