Makefile: delete HOSTFC and FC_FOR_BUILD

This definition of HOSTFC is completely wrong.

"$(HOSTLD)" should be "$(HOSTFC)".  Also, "echo" always succeeds, so
"which g77 || type -p g77 || echo gfortran" is never run.

Anyway, HOSTFC is most likely set to "/use/bin/ld" and nobody has
complained about it before me, so I guess it is not used at all.

At least grepping HOSTFC, FC_FOR_BUILD did not hit any packages.
Drop HOSTFC and FC_FOR_BUILD.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>