[gfortran] Let f951 generate type infos for SELECTED_*_KIND

[Tobias Schlüter]

Tobias Schlüter wrote:
> This straightforward patch implements this. The only non-trivial part was
> finding out how to pass the new option to f951 during the build, but this
> turned out to be trivial as well, after I had found the correct driver option.

Unfortunately, I hadn't thought aobut multilibbed targets. These call the same
compiler, but with different options, e.g. 'f951 -m32' vs. 'f951 -m64'. This
of course breaks my patch. There's no -Wc options, which would allow running
"$(F77COMPILE) -Wc,-output-real-type-infos", and I also didn't find another
solution. If anybody knows an elegant solution for how to run the compiler as
opposed to the compiler driver with the correct options, I'm listening.

Thanks,
- Tobi