Add -mminimal-toc to CFLAGS on powerpc64 to fix linking:
/usr/bin/ld: rigs/flrig-TS950.o(.text+0x1c40): sibling call optimization to _ZN7rigbaseD2Ev' does not allow automatic multiple TOCs; recompile with -mminimal-toc or -fno-optimize-sibling-calls, or make _ZN7rigbaseD2Ev' extern
PR: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=237816