The following file under git hub repo has not been updated for quite some time:-
swift-llvm/Threading.h at stable · apple/swift-llvm · GitHub
Due to this changes made in ⚙ D56382 Change llvm call once check for building Swift for PowerPC(ppc64le) are not reflecting yet, hence the Swift toolchain build is still failing on ppc64le, inspite of being fixed.
Any timeline for this to be updated?
Did you try the parallel branches that automatically track upstream LLVM changes? For swift, that is the master-next branch. For llvm/clang, you need to checkout the upstream-with-swift branches. Please keep in mind that testing of these branches is minimal, so there might be other problems. If you want a change cherry-picked into the Swift stable branch of LLVM, try asking @Bob_Wilson.
The stable branch is automatically kept in sync with the latest release branch (currently swift-5.1-branch), so you should never need to update stable directly.
Which just means that you need your patch to get cherry-picked into swift-5.1-branch, but I think that should be acceptable.