Bug 1285860 - Add python/mozbuild at beginning of sys.path; r=glandium

We want local source directory paths to take precedence over system
paths so system installed packages don't get used.

MozReview-Commit-ID: FIZ0RxqZj78

--HG--
extra : rebase_source : e8d484ea0c8a0bdb1df10375317f6b2c349b9162

configure.py

@@ -12,7 +12,7 @@
 
 
 base_dir = os.path.abspath(os.path.dirname(__file__))
-sys.path.append(os.path.join(base_dir, 'python', 'mozbuild'))
+sys.path.insert(0, os.path.join(base_dir, 'python', 'mozbuild'))
 from mozbuild.configure import ConfigureSandbox