This package does not respect system's AS: x86_64-pc-linux-gnu-as From the build log: as --64 -o /var/tmp/portage/dev-lang/fpc-2.6.2/work/fpcbuild-2.6.2/fpcsrc/rtl/units/x86_64-linux/prt0.o x86_64/prt0.as
Fixed in CVS.