[clang] [Clang] Warn on deprecated specializations used in system headers. (PR #70353)

[Kamau Bridgeman via cfe-commits]

kamaub wrote:

This patch exposes the use of deprecated specializations in the third-party Google Test suite built via this buildbot https://lab.llvm.org/staging/#/builders/104/builds/106/steps/6/logs/stdio. The bot ordinality isn't in staging, it is there temporary while we test and update its configuration and intend to move it back to the main server once it builds libcxx and libcxxabi cleanly.

Can you provide any insight on how to resolve these warning? Would specifying`-Wno-deprecated-declarations>` specified in the gtest `CMakeList.txt` appropriate to temporarily handle them until the third-party unittest can be updated?

https://github.com/llvm/llvm-project/pull/70353