[llvm] [Offload] Run unit tests as a part of check-offload (PR #156675)

[Jan Patrick Lehr via llvm-commits]

jplehr wrote:

It appears that this breaks the ability to do `LIT_FILTER=offload/some-test ninja check-offload` with a test coming from the lit tests.

Leaving this here as an observation and something we likely want to fix at some point.

https://github.com/llvm/llvm-project/pull/156675