[flang] [clang] [flang][driver] Allow explicit specification of -lFortran_main (PR #78152)

[Tom Eccles via cfe-commits]

tblah wrote:

I agree that the documentation says not to do this, but existing common build configurations are doing it anyway. For example, building netcdf-parallel (https://github.com/Parallel-NetCDF/PnetCDF) using spack (https://spack.io/).

netcdf-parallel uses autotools. I haven't tried another autotools project to see if it has the same problem.

Of course the long term solution will be to fix autotools (or whatever the culprit is), but I worry it could take a long time for such patches to filter out to distros. In the meantime, I think it is a bad user experience to fail builds with a cryptic linker error.

https://github.com/llvm/llvm-project/pull/78152