[llvm] [Flang][LLVM] Remove leftover CMake for old flang handling (PR #137049)

[Michael Kruse via llvm-commits]

Meinersbur wrote:

Do you mean #130975?

LLVM_ENABLE_RUNTIMES=openmp and LLVM_ENABLE_PROJECTS=openmp are both still supposed to work. It just fixed a dependency problem with LLVM_ENABLE_RUNTIMES=openmp (and updates some CMake messages to clarify that there are two ways to build it.

https://github.com/llvm/llvm-project/pull/137049