[clang] Fix some static initialization race-conditions (PR #181367)

[via cfe-commits]

github-actions[bot] wrote:

<!--PREMERGE ADVISOR COMMENT: Windows-->
# :window: Windows x64 Test Results

* 52047 tests passed
* 959 tests skipped
* 474 tests failed

Failed tests and their output was too large to report. Download the build's log file to see the details.

If these failures are unrelated to your changes (for example tests are broken or flaky at HEAD), please open an issue at https://github.com/llvm/llvm-project/issues and add the `infrastructure` label.

https://github.com/llvm/llvm-project/pull/181367