[llvm] [ci][llvm] Run cross-project-tests on llvm/ changes (PR #188522)

[Michael Buch via llvm-commits]

Michael137 wrote:

So the tests are being run, it's just that GDB and LLDB don't exist on the host. So we're getting:
```
2026-03-27T13:32:09.0317017Z No GDB found on host. Skipping tests that require GDB.
2026-03-27T13:32:09.2914223Z Found LLDB version 'None'
```

But we do get the benefit of running most of the other tests.

So I think we can land this and sort out the LLDB/GDB thing in a follow-up

https://github.com/llvm/llvm-project/pull/188522