[clang] [clang] Diagnose use of deprecated template alias (PR #97619)

[Louis Dionne via cfe-commits]

ldionne wrote:

@premanandrao  There are instructions here: https://libcxx.llvm.org/BuildingLibcxx.html#bootstrapping-build

You can also use e.g. `run-buildbot` for this job: https://github.com/llvm/llvm-project/blob/c7961538ff5c73ad03cbf2470e56cdc10cedc83b/libcxx/utils/ci/run-buildbot#L366
You will probably need to modify a few things like maybe remove the mentions of `ccache`.

https://github.com/llvm/llvm-project/pull/97619