Make git recipe api add depot_tools to PATH

recipe_modules/git/example.expected/count-objects_delta.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_MODULE[depot_tools::git]/resources/git_setup.py",
       "--path",
       "[SLAVE_BUILD]/src",
       "--url",
       "https://chromium.googlesource.com/chromium/src.git"
@@ skipping 24 matching lines @@
   {
     "cmd": [
       "git",
       "retry",
       "fetch",
       "origin",
       "master",
       "--recurse-submodules"
     ],
     "cwd": "[SLAVE_BUILD]/src",
+    "env": {
+      "PATH": "RECIPE_PACKAGE_REPO[depot_tools]:%(PATH)s"
+    },
     "name": "git fetch"
   },
   {
     "cmd": [
       "git",
       "count-objects",
       "-v"
     ],
     "cwd": "[SLAVE_BUILD]/src",
     "name": "count-objects after git fetch",
@@ skipping 186 matching lines @@
     ],
     "cwd": "[SLAVE_BUILD]/src",
     "name": "git bundle"
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]