go: add build_style=go to avoid code duplication

[ericonr]

The GOARCH selection snippet was duplicated in the go build_style script
for environment variables and in the go template itself. Furthermore,
there were discrepancies between the two snippets, which have been
fixed.

This makes the go template leaner, and makes both cases more robust (changes to GOARCH selection can be done in a single place).

[ericonr]

Seems some builds failed with timeouts, with others the issue was memory consumption during the bootstrap process:

cc1plus: out of memory allocating 262144 bytes after a total of 3915776 bytes

[Johnnynator]

This adds go to hostmakedepends and therefore results in a build loop for noncross architectures.

[ericonr]

This adds go to hostmakedepends and therefore results in a build loop for noncross architectures.

Yeah, I was messing with it and noticed this issue when building for a second time. Do you know if I could just source the c/e/build_style/go.sh file? From what I read of the manual, there isn't any variable that points to the directory where xbps-src is located and I don't know if it's possible for the script to be run from anywhere or if it's always supposed to be run as ./xbps-src.

[q66]

broken does not work in environment, it's not a variable

this PR doesn't really make sense

[q66]

ec937e4 and 927e790 addressed the functional concerns of this, other than that it doesn't really make sense to set build-style here as there is too much of a mismatch and attempting to merge them would create more code than remove.