cmd/go, cmd/link: support -buildmode=shared on FreeBSD

[kolbycrouch]

Hello. I noticed recently when trying to build a shared copy of std, that cmd/go and cmd/link don't support shared linking on FreeBSD for any architecture.

After simply adding FreeBSD/amd64 to the case in cmd/go/internal/work/init.go and adding a case for FreeBSD in cmd/link/internal/ld/config.go, I was able to get a libstd.so and link a hello world program dynamically. The hello world program worked as well.

I was wondering if there was some known issue with dynamic linking on FreeBSD, or if it was simply overlooked.

[ianlancetaylor]

It was most likely simply untested. Want to send a patch?

[gopherbot]

Change https://golang.org/cl/157682 mentions this issue: cmd/go,cmd/link: Adds shared linking support for FreeBSD/amd64