[llvm] [Github] Build PGO optimized toolchain in container (PR #80096)

[Aiden Grossman via llvm-commits]

boomanaiden154 wrote:

> #78879 should make it possible to optimize the build further.

Yep. My plan is to adjust this script once that lands and do some proper compile time experiments.

https://github.com/llvm/llvm-project/pull/80096