This fixes a bug whereby the Guix importer considers files like .f.* to be
Fortran files.
The expression "\\.f(90|95)?" would match a lot of files containing ".f"
although they are not Fortran files. Instead we should only consider files
with this *suffix*.
* guix/import/cran.scm (directory-needs-fortran?): Only check for suffixes.
Co-authored-by: Ricardo Wurmus <rekado@elephly.net>