Roll recipe dependencies (nontrivial).

scripts/slave/recipes/ios/try.expected/icu_patch.json

 [
   {
     "cmd": [
       "RECIPE_PACKAGE_REPO[build]/scripts/slave/ios/host_info.py",
       "--json-file",
       "/path/to/tmp/json"
     ],
     "name": "host and tools info",
     "~followup_annotations": [
       "@@@STEP_TEXT@<br />OS X 1.2.3, Xcode 6.7.8 (5D342509a)@@@",
@@ skipping 54 matching lines @@
       "--output_json",
       "/path/to/tmp/json",
       "--revision",
       "src@HEAD",
       "--revision",
       "src/third_party/icu@HEAD",
       "--output_manifest"
     ],
     "cwd": "[BUILDER_CACHE]/ios_simulator",
     "env": {
-      "PATH": "%(PATH)s:RECIPE_PACKAGE_REPO[depot_tools]"
+      "PATH": "RECIPE_PACKAGE_REPO[depot_tools]:%(PATH)s"
     },
     "name": "bot_update",
     "~followup_annotations": [
       "@@@STEP_TEXT@Some step text@@@",
       "@@@STEP_LOG_LINE@json.output@{@@@",
       "@@@STEP_LOG_LINE@json.output@  \"did_run\": true, @@@",
       "@@@STEP_LOG_LINE@json.output@  \"fixed_revisions\": {@@@",
       "@@@STEP_LOG_LINE@json.output@    \"src\": \"HEAD\", @@@",
       "@@@STEP_LOG_LINE@json.output@    \"src/third_party/icu\": \"HEAD\"@@@",
       "@@@STEP_LOG_LINE@json.output@  }, @@@",
@@ skipping 397 matching lines @@
   {
     "cmd": [],
     "name": "trigger"
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]