[llvm] [BOLT] Fix LLVM_APPEND_VC_REV support (PR #142410)

[Paschalis Mpeis via llvm-commits]

paschalis-mpeis wrote:

This appears to have happened around #97130. Shortly before, around commit b037d0f0e5f6c7ab528fe3ed9d855f0d770c6709 this flag was respected.

There is no reliable way to check this within LLVM itself, but I will add a validation step on the buildbot to track whether the NFC comparisons are working as expected (ie the commit SHA as well the GNU IDs).
That could issue a warning (and not flunk). In terms of time it'll be essentially free.

https://github.com/llvm/llvm-project/pull/142410