goma_util: Bypass path_util.ToChrootPath calls.

The path_util module depends on the chroot living at SOURCE_ROOT/chroot.
This is not a valid assumtion for the Luci builders, and the path_util
calls fail. Manually build out the inside-chroot paths that are needed
to bypass the path_util module until it can handle the non-default
chroot case.

BUG=chromium:1013948
TEST=run_tests

Change-Id: I31b28d6c525ef470f059aef4fafc5fdc389b791f
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/1860372
Commit-Queue: Alex Klein <saklein@chromium.org>
Tested-by: Alex Klein <saklein@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
diff --git a/api/controller/controller_util.py b/api/controller/controller_util.py
index 5eb44cb..af76a6b 100644
--- a/api/controller/controller_util.py
+++ b/api/controller/controller_util.py
@@ -7,8 +7,6 @@
 
 from __future__ import print_function
 
-import os
-
 from chromite.api.gen.chromiumos import common_pb2
 from chromite.cbuildbot import goma_util
 from chromite.lib import portage_util
@@ -65,7 +63,7 @@
                           chroot_message.goma.goma_client_json,
                           stage_name='BuildAPI',
                           chromeos_goma_dir=chromeos_goma_dir,
-                          chroot_tmp=os.path.join(path, 'tmp'))
+                          chroot_dir=path)
 
   return Chroot(path=path, cache_dir=cache_dir, chrome_root=chrome_root,
                 env=env, goma=goma)