games/freedoko: Respect LDFLAGS and mark LLD_UNSAFE

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

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

./sound/alut.o:(Sound::Alut::~Alut())

http://beefy12.nyi.freebsd.org/data/head-amd64-default/p474767_s336359/logs/freedoko-0.7.16.log

PR: 226980
Reported by: emaste, pkg-fallout