[llvm] [llvm] Add support for running tests as root (PR #75285)

[Aiden Grossman via llvm-commits]

https://github.com/boomanaiden154 approved this pull request.

LGTM. Please wait for @MaskRay / others to chime in though.

Thanks for putting this together. Given the CI constraints, I think there's a really compelling case for adding this in.

https://github.com/llvm/llvm-project/pull/75285