Handle non binary bundles and environment variables in include paths. 

BUG=chromium:236517
TEST=Added test to non-strs-flattened-to-env and postbuilds
Review URL: https://codereview.chromium.org/14617004/

Patch from Justin Cohen <justincohen@google.com>!

git-svn-id: http://gyp.googlecode.com/svn/trunk@1622 78cadc50-ecff-11dd-a971-7dbc132099af