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

[via llvm-commits]

zmodem wrote:

> The price for ThinLTO is surprisingly high (in memory usage too I guess), and compared to PGO alone, the added value is pretty low in this case. Considering the numbers, I agree with you to only do PGO, as it's almost "free".

Part of the high cost is that it applies not just to clang, lld, etc., but all the binaries, including the ones only used for testing.

> If we go with the PGO only version, it could be nice to directly factorize this for all architecture (do_build_libxml function provides an example).

Agreed, but can we do it in a follow-up when applying this to more targets? (For example, the PGO part should work for x86 too.)

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