Imported from GitHub PR https://github.com/abseil/abseil-cpp/pull/1412

In Clang, an `-Xarch_` compiler flag indicates that its successor only applies to the specified platform (e.g., `-Xarch_x86_64 -maes`). This is used in `absl/copts/AbseilConfigureCopts.cmake` to selectively enable hardware AES support on Apple platforms.

However, when generating pkg-config files, those `-m` flags are filtered out, while the `-Xarch_` flags that precede them are left untouched. This led to the error reported in #1408.

Fix that by filtering out each `-Xarch_` flag with its successor at once.

Fixes #1408.
Merge 89d20ab816b7cead56f05d5a6bc5146d1c4f4335 into 34604d5b

Merging this change closes #1412

COPYBARA_INTEGRATE_REVIEW=https://github.com/abseil/abseil-cpp/pull/1412 from ZhongRuoyu:xarch-pkgconfig 89d20ab816b7cead56f05d5a6bc5146d1c4f4335
PiperOrigin-RevId: 606730193
Change-Id: I3e177a56721acd3145fd03c64102741898afd2a5