[llvm] [Flang-rt] Remove COMPILE_ONLY from flang-rt CMake file. (PR #169534)

[Joseph Huber via llvm-commits]

https://github.com/jhuber6 approved this pull request.

Thanks, sorry about that mix-up. I think the original reason I did this is because it emitted warnings sometimes, but we can just ignore those separately if it's an issue

https://github.com/llvm/llvm-project/pull/169534