[llvm] [lit] Add --wtt-output option to report results in WTT (.wtl) format (PR #211066)

[Yasser Khan via llvm-commits]

yassermkhan wrote:

> I feel the test coverage can be done much more simply by just using the normal lit primitives with `ShTest` rather than a custom format.

The custom format follows the existing reporter tests like `test-output-resultdb.py` , `test-output-micro-resultdb.py`, and `xunit-output.py`. They all drive their reporter through the same DummyFormat + .ini inputs rather than ShTest.

https://github.com/llvm/llvm-project/pull/211066