[clang] [flang] [flang][driver] Separate the actions of the `-emit-fir` and `-emit-mlir` options (PR #139857)

[via cfe-commits]

https://github.com/jeanPerier commented:

While I understand the goal, I also have some issues with the genericity of the name while there is no single MLIR core dialect. How would you make a difference between lowering to different level of representation that the core dialect offer: affine, linalg, scf, cf, memref, tensor, llvm dialect?

I have no problem having some `-emit-llvm-dialect` option though, on the contrary.

https://github.com/llvm/llvm-project/pull/139857