environment/build-style/go.sh: specify a default set of archs
environment/build-style/go.sh: specify a default set of archs

This is necessary so that crossbuilds to unsupported architectures
are not actually attempted. There is a default archs set which
covers all architectures supported by the official compiler,
and setting it in the template can be used to restrict it more.

Also, add missing GOARCHs. These are irrelevant to whether we
can currently build for that arch or not. Just keep it around
as a list of potential archs to support. These are taken from
gccgo, and in case support for anything is added in the official
compiler, they should match.

necrophcodr/void-packages,necrophcodr/void-packages,necrophcodr/void-packages,necrophcodr/void-packages,necrophcodr/void-packages