[libcxx-commits] [libcxxabi] [libc++abi] Use target_compile_options to pass LIBCXXABI_ADDITIONAL_COMPILE_FLAGS (PR #96112)

[Zibi Sarbinowski via libcxx-commits]

zibi2 wrote:

Unfortunately this breaks our buids which use `LIBCXXABI_ADDITIONAL_COMPILE_FLAGS`. 

The `set_target_properties()` sets COMPILE_OPTIONS which add these flags libcxx but intended to be libcxxabi flags only.
I believe this is beause libcxx depends on building libcxxabi first and the options set during libcxxabi build are also used for libcxx. Prior to this commit they were added only to LIBCXXABI_COMPILE_FLAGS using this macro:

```
macro(add_compile_flags)
  foreach(f ${ARGN})
    list(APPEND LIBCXXABI_COMPILE_FLAGS ${f})
  endforeach()
endmacro()
```

@ldionne  Can this be reverted back until we find an alternative way to separate `LIBCXXABI_COMPILE_FLAGS` from `LIBCXX_COMPILE_FLAGS`? 

https://github.com/llvm/llvm-project/pull/96112