[PATCH 3 of 5] setup: move environment computation into a helper function

[Augie Fackler]

On Mon, Jun 26, 2017 at 11:37:42AM -0700, Adam Simpkins wrote:
> # HG changeset patch
> # User Adam Simpkins <simpkins at fb.com>
> # Date 1498501890 25200
> #      Mon Jun 26 11:31:30 2017 -0700
> # Node ID f12d9578f43cc253f46a5dce2c7e288cac0fdada
> # Parent  a687d5c7ac85481471d973aa06c6fd4b1dad91f0
> setup: move environment computation into a helper function

queued patces 1-3, thanks (you only need to rebase and resend 4 and 5)