[llvm] Use thinlto and pgo for x86_64 windows release packaging (PR #71067)

[via llvm-commits]

zmodem wrote:

+cc @pbo-linaro 

This has been on the todo list a long time.

Why not x86 also? We can't do bootstrapping thinlto because the linker will run out of memory. I think it's okay to focus on x86_64 for performance. Maybe we can even stop building the 32-bit binaries eventually.

https://github.com/llvm/llvm-project/pull/71067