[llvm] [LLD] Avoid non-deterministic relocations processing. (PR #107186)

[Fangrui Song via llvm-commits]

MaskRay wrote:

Shall we restore the old `execute` behavior before
https://reviews.llvm.org/D148728:  run the task in the main thread?

The downside is that we cannot keep the `threadIndex != UINT_MAX` assertion. I feel that the value of the assertion is low. If needed, the assertion can be restored using a different mechanism.

https://github.com/llvm/llvm-project/pull/107186