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

[Joseph Huber via llvm-commits]

jhuber6 wrote:

> Without trying out, I think it is still needed. `LLVM_TOOL_<project>_BUILD` is set whenever `LLVM_ENABLE_PROJECTS=<project>`. `extra_deps` ensures that flang and the Fortran built modules are built before OpenMP tries to build `omp_lib.mod` using flang and the builtin modules. I don't know what you mean by "old flang handling"

I thought that handling was moved into the runtimes job itself as in https://github.com/llvm/llvm-project/pull/137035.

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