emulators/fs-uae: fix build on non-x86

JIT is enabled by default everywhere, which causes fail on e.g. powerpc64:
configure: error: in `/wrkdirs/usr/ports/emulators/fs-uae/work/fs-uae-3.0.2':
configure: error: JIT is not supported on powerpc64-portbld-freebsd12.1

Make JIT option available on all architectures so that --disable-jit is properly passed when the option is disabled.

MFH: 2020Q2 (fix build blanket)