[llvm] Make sure all matrix options are run in libc premerge testing (PR #146162)

[Aiden Grossman via llvm-commits]

boomanaiden154 wrote:

> It does seem to be taking a lot longer now to complete all the Linux runs, presumably because there are now four builds running with the same Linux config.

Adding additional builds shouldn't hurt much. They should all run in parallel. Adding a new configuration that takes longer (like a debug configuration) could result in the total workflow taking longer though.

https://github.com/llvm/llvm-project/pull/146162