Minor fixes

The miner now pulls updates as intended.

Also make release and make xc should work as intended too, which was not previously the case.

I'm not sure how build flags work in goxc, setting -build-tags=release wasn't doing the trick. So I also modified the build tags in buildrelease.go as a workaround. It's probably for the better anyway, now someone naively running go install won't be greeted with an excessive amount of errors, but instead will be greeted with a binary that has release constants.