[llvm] [llvm][llvm-lit] Add option to create unique result file names if results already exist (PR #112729)

[David Spickett via llvm-commits]

DavidSpickett wrote:

Right now ci does `ninja check-x check-y check-z etc.`. This means that the final part of the log is just the results of the final check-target, which might have passed but an earlier one didn't.

This feature will help me fix that by creating an aggregated report from which you can see right away which tests failed across the whole build.

https://github.com/llvm/llvm-project/pull/112729