[xb] Fall back to normal clone if shallow fails

xenia-build

@@ -417,6 +417,18 @@ def git_is_repository():
 def git_submodule_update():
     """Runs a git submodule init and update.
     """
+    ret = shell_call([
+        'git',
+        '-c',
+        'fetch.recurseSubmodules=on-demand',
+        'submodule',
+        'update',
+        '--init',
+        '--depth=1',
+        '-j', str(os.cpu_count()),
+        ], throw_on_error=False)
+    if ret != 0:
+        print('Shallow submodule update failed, falling back to normal...')
         shell_call([
           'git',
           '-c',
@@ -424,8 +436,6 @@ def git_submodule_update():
           'submodule',
           'update',
           '--init',
-        #'-j', args['j'], # These would be faster if they worked
-        #'--depth 1',
           ])