games/flightgear: set LLD_UNSAFE
Prevent Flightgear from linking using lld as it fails with errors like:
/usr/bin/ld: error: cannot preempt symbol: alcGetIntegerv
defined in /usr/local/lib/libopenal.so
referenced by audio_openal.caudio_openal.c.o:(openal_input)
due to preemption of symbols with protected visibility in a shared object.
See also PR #219089 for more details.
Submitted by: emaste