Use GOPATH/pkg/depcache instead of GOPATH/depcache

[sdboyer]

Per discussion in #77

This is a potentially bikesheddy (golang/go#17262, golang/go#4719, etc.), so let's get some 👍 before going ahead

[jessfraz]

ooo interesting I didn't know about golang/go#4719, LGTM but im sure adg knows more

[freeformz]

$GOPATH/pkg/depcache seems strange to me, but not too strange.

[jessfraz]

yeah it kinda seems like ls-ing in the dir primarily with folders named after archs is odd but idk

[sdboyer]

i tend to agree that it's a bit odd semantically, but i'm fine with doing it for now b/c it's an easy thing for us to change later, and it solves the $HOME/depcache problem that we currently have

[jessfraz]

ooo makes sense