[llvm] [MC][Support] Track macro definition locations for improved diagnostics (PR #198936)

[Fangrui Song via llvm-commits]

MaskRay wrote:

> @MaskRay Any suggestions who else could review this if you are too busy?

I like the direction of the patch but I'm worried about the AI slop.

https://github.com/llvm/llvm-project/pull/198936