[Bug fortran/124484] Coarray test error on some older glibc due to missing -lrt

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=124484

--- Comment #8 from Richard Biener <rguenth at gcc dot gnu.org> ---
Maybe link with -pthread and let specs sort out the details?  We should be
always linking using GCC.