[llvm] [libcxx] [ci] Update Clang on Windows (PR #152206)

[Aiden Grossman via llvm-commits]

boomanaiden154 wrote:

> This release of llvm-mingw is the first release to be built with PGO, making it significantly faster for the CI runs (on par with the clang-cl cases); running the current tests in around 1 h rather than 1 h 20 min.

What are you using for perf training? And do you have ThinLTO enabled?

I've been thinking about PGO optimizing a toolchain for the Linux builds, but not sure if it's worth the complexity given the normal container image has so many different toolchain versions and in so many different configurations.

https://github.com/llvm/llvm-project/pull/152206