Fix compilation error on AMD64, thanks to Frans Pop
<elendil@planet.nl> for the report, thanks to Mooie <mooie@cow.se> for
the fix:
* Makefile (FORTIFY): Replaced "-pie" with "-fPIC".
(LINK_FORTIFY): Renamed to "LINK_FORTIFY_LD" and added "-fPIE".
(LINK_FORTIFY): New; set to "-pie".
(LDFLAGS): Also include "$(LINK_FORTIFY)" (unmodified).