games/stockfish: update to 10

Add LDFLAGS+= -fuse-ld=lld
so the port builds regardless of the linker differences between FreeBSD
releases.

Not much in the release notes:
http://blog.stockfishchess.org/post/180691011237/stockfish-10

SF 10 improves by about 50 ELO in self-play compared to SF 9.

PR: 234035
Submitted by: execve@gmail.com (maintainer)