[clang] [lld] [llvm] Compute GUIDs once and store in metadata (PR #184065)

[Alan Phipps via cfe-commits]

evodius96 wrote:

Hello! This commit appears to be breaking our downstream toolchain support for LTO, particularly constant merging. I'll try to come up with a reproducer, but it's difficult because we use a proprietary linker.  However, I wanted to give you a heads-up.

https://github.com/llvm/llvm-project/pull/184065