pw_env_setup: Skip submodule check for repo tool

Skip the submodule presence check when using the Android Repo Tool. This
usually isn't an issue, but it becomes one when there's no top-level
project in the repo workspace.

Change-Id: I5fe0d4f75f855c1214df676108acdfd619b170bd
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/62140
Pigweed-Auto-Submit: Rob Mohr <mohrr@google.com>
Commit-Queue: Auto-Submit <auto-submit@pigweed.google.com.iam.gserviceaccount.com>
Reviewed-by: Keir Mierle <keir@google.com>
diff --git a/pw_env_setup/py/pw_env_setup/env_setup.py b/pw_env_setup/py/pw_env_setup/env_setup.py
index 931a085..1c726e8 100755
--- a/pw_env_setup/py/pw_env_setup/env_setup.py
+++ b/pw_env_setup/py/pw_env_setup/env_setup.py
@@ -298,6 +298,10 @@
     def _check_submodules(self):
         unitialized = set()
 
+        # Don't check submodule presence if using the Android Repo Tool.
+        if os.path.isdir(os.path.join(self._project_root, '.repo')):
+            return
+
         cmd = ['git', 'submodule', 'status', '--recursive']
 
         for line in subprocess.check_output(