cmd/dist: check more GOOS/GOARCH combinations in mkdeps.bash
The current mkdeps.bash just checks for dependencies for GOOS=windows
with the current GOARCH. This is not always accurate as some package
imports only happen on specific GOOS/GOARCH combinations. Check a
selected, easily changed, combination of GOOS/GOARCH values.
This generates a deps.go identical to the one in the repository today.