[clang] [flang] Allow disabling of types from the command line (PR #107126)

[Andrzej Warzyński via cfe-commits]

https://github.com/banach-space commented:

What's the end goal here? To add an option for every possible bit-width? If yes, then these options should take bit width as parameters.

Btw, does GFortran implement anything like this? If yes, are you making sure that the semantics in Flang are consistent? Please also add help text. 

https://github.com/llvm/llvm-project/pull/107126