[llvm] [lit] Add support to print relative paths when outputting test names (PR #154317)

[Nikita Popov via llvm-commits]

https://github.com/nikic commented:

Any reason not to enable this by default?

I guess one unfortunate interaction here would be with `ninja -Cbuild check-llvm`, which would presumably print tests relative to `build` instead of the root directory?

https://github.com/llvm/llvm-project/pull/154317