cmd/go: add a way to support GOFLAGS=-ldflags='-w -s' #29096
Description
The previous documentation example mentioned GOFLAGS='-ldflags=-w -ldflags=-s', which does something completely different. The second per-package flag overrides the first, so the linker ends up being called with just -s and not -w -s.
There should be a way to do go build -ldflags='-w -s' via GOFLAGS. This can either be done by tweaking GOFLAGS, or by tweaking per-package flags - I personally don't mind, as long as there's a way to achieve it.