fail gracefully if gclient-new-workdir.py is called in non-git env

Bug: 345486495
Change-Id: Ide3f8e6a649694a5e1f730ee0e159f928e287c4e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/5608427
Commit-Queue: Josip Sokcevic <sokcevic@chromium.org>
Reviewed-by: Josip Sokcevic <sokcevic@chromium.org>
Auto-Submit: Yiwei Zhang <yiwzhang@google.com>

gclient-new-workdir.py

@@ -14,6 +14,7 @@ import subprocess
 import sys
 import textwrap
 
+import gclient_utils
 import git_common
 
 
@@ -23,6 +24,9 @@ def parse_options():
             'ERROR: This script cannot run on Windows because it uses symlinks.'
         )
         sys.exit(1)
+    if gclient_utils.IsEnvCog():
+        print('ERROR: This script cannot run in non-git environment.')
+        sys.exit(1)
 
     parser = argparse.ArgumentParser(description='''\
       Clone an existing gclient directory, taking care of all sub-repositories.