Roll recipe dependencies (nontrivial).

scripts/slave/recipes/v8.expected/full_client_dart_fyi_v8_win_release.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_PACKAGE_REPO[build]\\scripts\\slave\\kill_processes.py"
     ],
     "name": "taskkill"
   },
   {
@@ skipping 11 matching lines @@
       "[GIT_CACHE]",
       "--output_json",
       "/path/to/tmp/json",
       "--revision",
       "v8@refs/branch-heads/4.2:20123",
       "--no_shallow",
       "--output_manifest",
       "--with_branch_heads"
     ],
     "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@    \"v8\": \"refs/branch-heads/4.2:20123\"@@@",
       "@@@STEP_LOG_LINE@json.output@  }, @@@",
       "@@@STEP_LOG_LINE@json.output@  \"manifest\": {@@@",
@@ skipping 278 matching lines @@
       "{\"blamelist\": [\"cool_dev1337@chromium.org\", \"hax@chromium.org\"], \"branch\": \"4.2\", \"buildername\": \"v8-win-release\", \"buildnumber\": 571, \"mastername\": \"client.dart.fyi\", \"parent_buildername\": null, \"recipe\": \"v8\", \"revision\": \"20123\", \"slavename\": \"TestSlavename\", \"workdir\": \"/path/to/workdir/TestSlavename\"}"
     ],
     "name": "package build"
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]