Unless I force the Fortran compiler through --with-g77, configure fails to
find and use the installed g77. I would submit a patch for configure.in,
but I can't quite follow the logic in configure.in.
$ ./configure
creating cache ./config.cache
[...]
checking for main in -lm... yes
checking for g77... /usr/local/gnu/bin/g77
checking for fort77... (cached) /usr/local/gnu/bin/g77
checking for f77... (cached) /usr/local/gnu/bin/g77
checking for f90... (cached) /usr/local/gnu/bin/g77
checking for xlf... (cached) /usr/local/gnu/bin/g77
checking for cf77... (cached) /usr/local/gnu/bin/g77
checking for fc... (cached) /usr/local/gnu/bin/g77
checking for f2c... no
configure: error: Neither an F77 compiler nor f2c found
$