depot_tools: use ninja.exe instead of just ninja on Windows

BUG=437264

Review URL: https://codereview.chromium.org/1778243008

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@299267 0039d316-1c4b-4281-b951-d872f2087c98

recipe_modules/depot_tools/__init__.py

+DEPS = [
+  'recipe_engine/platform',
+]

recipe_modules/depot_tools/api.py

@@ -11,4 +11,5 @@ class DepotToolsApi(recipe_api.RecipeApi):
 
   @property
   def ninja_path(self):
-    return self.package_repo_resource('ninja')
+    ninja_exe = 'ninja.exe' if self.m.platform.is_win else 'ninja'
+    return self.package_repo_resource(ninja_exe)