emulators/tuxnes: set LLD_UNSAFE on i386

This port builds and runs a build tool, which segfaults when lld is the
i386 system linker:

cc -O2 -pipe -fstack-protector -fno-strict-aliasing -pipe -Wall

-I/usr/local/include  -I/usr/local/include -fstack-protector
-o comptbl  comptbl.o  -lm -lz -lXext -lXpm   -lSM -lICE -lX11
-L/usr/local/lib

./comptbl
gmake[1]: *** [Makefile:414: compdata] Segmentation fault (core dumped)

PR: 214864
Approved by: portmgr (lld blanket)
Sponsored by: The FreeBSD Foundation