thorpej@shagadelic.org said:
> maybe an   optional "Fortran run-time" set

Afaict that would not just be run-time but compile-time.
At least the compiler backend is linked against mpfr and gmp:
[from an old gcc4 installation]
$ ldd /usr/local/libexec/gcc/i386-unknown-netbsdelf3.99.15/4.1.0/f951
/usr/local/libexec/gcc/i386-unknown-netbsdelf3.99.15/4.1.0/f951:
        -lmpfr.1 => not found
        -lgmp.3 => not found
        -lc.12 => /usr/lib/libc.so.12

best regards
Matthias