Allows us to use the built-in suffix rules where appropriate.
FORTRAN -> FC (POSIX)
OPTS -> FFLAGS (POSIX)
DRVOPTS -> FFLAGS_DRV
NOOPT -> FFLAGS_NOOPT
LOADER -> FC (use the compiler driver for linking)
LOADOPTS -> LDFLAGS (POSIX)
ARCH -> AR (POSIX)
ARCHFLAGS -> ARFLAGS (POSIX)
cleanobj: Remove object files
cleanlib: Remove libraries
cleanexe: Remove test and example executables
cleantest: Remove test output and core dumps
clean: All of the above