Changed recipe_modules base paths to be abstract entities in their own right.

scripts/slave/recipes/skia/autoroll.expected/AutoRoll_stopped.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "[DEPOT_TOOLS]/gclient.py",
       "config",
       "--spec",
       "cache_dir = None\nsolutions = [{'deps_file': 'DEPS', 'managed': True, 'name': 'src', 'url': 'https://chromium.googlesource.com/chromium/src.git'}]"
     ],
@@ skipping 125 matching lines @@
       "\nimport shutil\nimport sys\nshutil.copy(sys.argv[1], sys.argv[2])\n",
       "Stopped",
       "arb_status.html"
     ],
     "name": "write arb_status.html"
   },
   {
     "cmd": [
       "python",
       "-u",
-      "[BUILD]/scripts/slave/recipe_modules/gsutil/resources/gsutil_wrapper.py",
+      "RECIPE_MODULE[gsutil]/resources/gsutil_wrapper.py",
       "--",
       "[DEPOT_TOOLS]/gsutil.py",
       "--force-version",
       "3.25",
       "--",
       "cp",
       "-a",
       "public-read",
       "arb_status.html",
       "gs://chromium-skia-gm/arb_status.html"
@@ skipping 42 matching lines @@
       "@@@STEP_LOG_LINE@python.inline@  params['last_roll_rev'] = full_hash(old)@@@",
       "@@@STEP_LOG_LINE@python.inline@  params['curr_roll_rev'] = full_hash(new)@@@",
       "@@@STEP_LOG_LINE@python.inline@@@@",
       "@@@STEP_LOG_LINE@python.inline@urllib2.urlopen(urllib2.Request(@@@",
       "@@@STEP_LOG_LINE@python.inline@    sys.argv[4],@@@",
       "@@@STEP_LOG_LINE@python.inline@    urllib.urlencode(params)))@@@",
       "@@@STEP_LOG_END@python.inline@@@"
     ]
   }
 ]