Build Go from source

[owenthereal]

I found that the prebuilt Go binaries downloaded by goenv are not cross-compilable. It reported missing some bash scripts.

Would it make sense for goenv to compile Go from source? Homebrew has an example.

[wfarr]

We could, but avoiding that if possible would be best.

I'd be open to allowing goenv-install to look for a flag to compile from source.