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

[Björn Pettersson via llvm-commits]

bjope wrote:

> Any reason not to enable this by default?

There are a lot more test cases that would be impacted if changing the default. I kind of wanted to get the functionality in place first, and then maybe we can toggle the default in the future. (Downside is ofcourse that someone need to review the option part and bikeshed on the command line option naming.)
 
> 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?

This is also kind of a reason why I did not just enable it by default. I've not tested and verified all kinds of scenarios, only some simpler tests using llvm-lit directly. And I have no idea if there are external tools (build bots etc) that tries to parse the output.

As mentioned above. If more people try this out without finding any huge problems we may consider changing the default in the future.

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