Add AIX to platforms that use "make" in gyptest.py

Review URL: https://codereview.chromium.org/24902002/
Patch from David Edelsohn <dje.gcc@gmail.com>!



git-svn-id: http://gyp.googlecode.com/svn/trunk@1742 78cadc50-ecff-11dd-a971-7dbc132099af