Mark games/openclonk LLD_UNSAFE

/usr/bin/ld: error: cannot preempt symbol: alGenSources

defined in /usr/local/lib/libopenal.so
referenced by C4MusicFile.cpp

CMakeFiles/openclonk.dir/src/platform/C4MusicFile.cpp.o:(C4MusicFileOgg::Play(bool, double))

http://beefy12.nyi.freebsd.org/data/head-amd64-default/p474767_s336359/logs/openclonk-8.1.log

Need to disable use of -flto too or the build would fail with

/usr/bin/ld.bfd: unrecognized option '-plugin'

PR: 226980
Reported by: emaste, pkg-fallout