[clang] [flang] [flang][driver] Add -fno-fortran-main (link time) option to remove Fortran_main from link line (PR #74139)

[Michael Klemm via cfe-commits]

mjklemm wrote:

> I know that it's extra work, but it's also super useful bit of documentation. And I would only rarely try to track the history beyond commit messages (there's just too much otherwise).

I can absolutely do that.  I'll craft some wording for the rationale behind that change and add it to the PR.

https://github.com/llvm/llvm-project/pull/74139