allow for out-of-tree builds

This adds a few missing build vars to the compile and makes it
so the code can be compiled out-of-tree.

BUG=None
TEST=`emerge-x86-alex ply-image` still works

Change-Id: Ifbec0b8706523c6ec61751f20d8fc874f76c97bb
Reviewed-on: https://gerrit.chromium.org/gerrit/48858
Reviewed-by: Daniel Erat <[email protected]>
Commit-Queue: Mike Frysinger <[email protected]>
Tested-by: Mike Frysinger <[email protected]>
2 files changed