Extended Description

lit has regressed a lot since the 4.0.0 release. We've managed to fix it in master, and it'd be really good to backport at least the most important fixes.

The minimal set needed to remove the regressions includes, in order:

309044 [lit] Fix UnboundLocalError for invalid shtest redirects
309071 [lit] Attempt to fix Python unittest adaptor logic
309120 Revert "[lit] Remove dead code not referenced in the LLVM SVN repo."
309122 [lit] Fix type error for parallelism groups
309140 Fix LIT test breakage
309227 [lit] Fix race between shtest-shell and max-failures tests

With those patches applied, lit tests reliably pass 100% again for me.

There are more potential backports but only those are strictly necessary to fix regressions on Gentoo. Others include a lot of Windows fixes, a few more corner case fixes and a CMake target to run lit tests. Those I'd rather leave to Brian's and Reid's judgement.