[lld] [LLD][COFF] Add -build-id flag to generate .buildid section. (PR #71433)

[Petr Hosek via llvm-commits]

petrhosek wrote:

Related to `__lld_buildid`, I'd prefer using a pair of symbols: `__lld_buildid_start` and `__lld_buildid_end`, so users of these symbols don't need to make assumptions about the size. This would also let us change the size in the future (if needed) without breaking all users.

In the past, I proposed a similar change [D76482](https://reviews.llvm.org/D76482) for `ld.lld` which generates a pair of synthetic symbols `__build_id_start` and `__build_id_end`. Ideally, we would revive and land that change, and also implement a similar change for `ld64.lld` so the code that's intended to support different file formats (like the compiler-rt profile runtime) can use the same logic to read the build ID rather than needing separate logic for each format.

https://github.com/llvm/llvm-project/pull/71433