You have to build the standard libraries and cross compilers first. I've seen this pair of zsh functions around. It will build the necessary bits and will also build for win/mac/linux/freebsd in simple projects and zip up the results for distribution (You can link to the raw zips then on github). For others looking to do this with go: https://github.com/colemickens/scripts/blob/master/dotfiles/... (Minor editting is needed due to some assumed values $ARCH, $OS, etc)
