Merge commit b84d773fd004 from llvm git (by Fangrui Song):
[Parallel] Revert sequential task changes https://reviews.llvm.org/D148728 introduced `bool Sequential` to unify `execute` and the old `spawn` without argument. However, sequential tasks might be executed by any worker thread (non-deterministic), leading to non-determinism output for ld.lld -z nocombreloc (see https://reviews.llvm.org/D133003). In addition, the extra member variables have overhead. This sequential task has only been used for lld parallel relocation scanning. This patch restores the behavior before https://reviews.llvm.org/D148728 . Fix #105958 Pull Request: https://github.com/llvm/llvm-project/pull/109084
This fixes the non-reproducibility we had noticed when linking our EFI
loaders, and for which we committed a workaround in f5ce3f4ef562.
MFC after: 3 days
(cherry picked from commit 54521a2ff93ae06c95c31f79f89dc23c9b51c20b)