add git_cache to base_paths

recipe_modules/path/config.py

Index: recipe_modules/path/config.py
diff --git a/recipe_modules/path/config.py b/recipe_modules/path/config.py
index 9db8b4ad48e27fcfaf49319cad85493dc411f50b..811c592b11040980aec2f091a5199dc34cb4f7fe 100644
--- a/recipe_modules/path/config.py
+++ b/recipe_modules/path/config.py
@@ -36,6 +36,7 @@ def BASE(c):
 def buildbot(c):
   c.base_paths['root'] = c.CURRENT_WORKING_DIR[:-4]
   c.base_paths['slave_build'] = c.CURRENT_WORKING_DIR
+  c.base_paths['git_cache'] = c.base_paths['root'] + ('slave', 'cache_dir')
   for token in ('build_internal', 'build', 'depot_tools'):
     c.base_paths[token] = c.base_paths['root'] + (token,)
   c.dynamic_paths['checkout'] = None
@@ -56,4 +57,5 @@ def kitchen(c):
   # TODO(phajdan.jr): Fully implement the kitchen config.
   c.base_paths['root'] = c.CURRENT_WORKING_DIR
   c.base_paths['slave_build'] = c.CURRENT_WORKING_DIR
+  c.base_paths['git_cache'] = c.base_paths['root'] + ('cache_dir',)
   c.dynamic_paths['checkout'] = None