[clang] [flang] [mlir] [flang] Add support for -mrecip[=<list>] (PR #142172)

[Slava Zakharin via cfe-commits]

https://github.com/vzakhari commented:

LGTM, though, I think we'd better reuse the code from `Clang.cpp`.  `flangFrontend` already depends on `clangDriver`, so we just need to export `ParseMRecip` and `getRefinementStep` from `clangDriver` (and probably replace their `Driver` argument with a `DiagnosticEngine` argument, so that it works for both clang and flang).

https://github.com/llvm/llvm-project/pull/142172