[llvm] [CI] Enable LTO linker plugin tests (PR #184076)

[Aiden Grossman via llvm-commits]

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

LGTM.

I can't imagine the linker plugin tests add any appreciable amount of time to the overall job.

https://github.com/llvm/llvm-project/pull/184076