Bug 1132562 - Use workspace directory so autoclobber can function with caches r=wcosta

- Move builder scripts into tree proper instead of baked into docker images

testing/taskcluster/scripts/builder/get-objdir.py

@@ -0,0 +1,20 @@
+#!/usr/bin/env python
+
+from __future__ import print_function
+import sys
+import os
+import json
+import subprocess
+from StringIO import StringIO
+
+gecko_dir = sys.argv[1]
+os.chdir(gecko_dir)
+
+result = subprocess.check_output(["./mach", "environment", "--format", "json"])
+environment = json.load(StringIO(result))
+
+topobjdir = environment["mozconfig"]["topobjdir"]
+if topobjdir is None:
+    topobjdir = sys.argv[2]
+
+print(topobjdir)