Enable riscv64 on go-snap (1.19/1.20/tip)

I'm afraid our current policy doesn't allow enabling riscv64 for snaps that pull source from repositories not controlled by Canonical, because our current builder environments aren't properly secured - doing this would mean that commits to https://go.googlesource.com/go could permanently compromise a riscv64 builder until the next time it's reflashed, potentially affecting multiple unrelated builds. We'll be able to relax this policy to be just like other architectures once PS6 is up and running.

Hi, does the rule apply to the released version, aka go119 and go120 snaps? Which is the same source with golang-{1.19,1.20} deb packages.

Thanks for reaching out. A colleague will follow-up.

I'm still not wholly comfortable, but I guess the external source being a tarball with a pinned checksum mitigates most of the risk. I've enabled riscv64 for go119 and go120.

Thanks!