Fix detection of GMS proguard.txt files

build/android/play_services/preprocess.py

Index: build/android/play_services/preprocess.py
diff --git a/build/android/play_services/preprocess.py b/build/android/play_services/preprocess.py
index 16fd3c46764585455c2ae5fd377eeba76c4beba8..e822c1a95bb221740fb94809123613b4b8191de1 100755
--- a/build/android/play_services/preprocess.py
+++ b/build/android/play_services/preprocess.py
@@ -220,7 +220,7 @@ def _EnumerateProguardFiles(root_dir, out_dir, gni_path):
   for client_dir in os.listdir(out_dir):
     proguard_path = os.path.join(
         out_dir, client_dir, 'proguard.txt')
-    if os.path.exists(os.path.dirname(proguard_path)):
+    if os.path.exists(proguard_path):
       rooted_path = os.path.relpath(proguard_path, root_dir)
       gni_lines.append('  "//{}",'.format(rooted_path))
   gni_lines.sort()