devel/libffcall: fix build on armv7
The port gets confused when compiling for ARM with no eabi to be found
in the target string. Add a FreeBSD special case to keep it happy.
Approved by: portmgr (build fix blanket)
MFH: 2025Q3
(cherry picked from commit c3d2880091d08b6860fe9a4431acb17f43391123)