2.1.1 - .exe handling for windows targets in go-build + go-release-binary

go build only auto-appends .exe when -o is unset. The catalog templates
always pass -o explicitly, so consumers adding windows/amd64 produced
an extension-less binary that's unrunnable on Windows without manual
rename. Both templates now append .exe when GOOS=windows.

No template inputs change. Consumers on 2.1.0 can bump to 2.1.1 with
no other edits.