[llvm] [Bolt] fix a wrong relocation update issue with weak references (PR #69136)

[Vladislav Khmelevsky via llvm-commits]

yota9 wrote:

So can we agree on merging this commit @rafaelauler ? I still think that this extra check is not useless and it fixes the problem :)

https://github.com/llvm/llvm-project/pull/69136