Add empty activity projects for benchmarking

empty-activity/README.google:

Name: Empty Android Activity
URL: https://github.com/christofferqa/empty_android_activity
Version: NA
Revision: 2d297ec3373dadb03cbae916b9feba4792563156
Date: Dec 16, 2021
License: Apache License 2.0


empty-compose-activity/README.google:

Name: Empty Android Compose Activity
URL: https://github.com/christofferqa/empty_android_compose_activity
Version: NA
Revision: 3c8111b8b7d6e9184049a07e2b96702d7b33d03e
Date: Dec 16, 2021
License: Apache License 2.0

Change-Id: I8228e485251da3589542f6363016ae615f2d08bc
diff --git a/.gitignore b/.gitignore
index 052f0a6..17af682 100644
--- a/.gitignore
+++ b/.gitignore
@@ -183,6 +183,10 @@
 third_party/opensource-apps/applymapping.tar.gz
 third_party/opensource-apps/chanu
 third_party/opensource-apps/chanu.tar.gz
+third_party/opensource-apps/empty-activity
+third_party/opensource-apps/empty-activity.tar.gz
+third_party/opensource-apps/empty-compose-activity
+third_party/opensource-apps/empty-compose-activity.tar.gz
 third_party/opensource-apps/friendlyeats
 third_party/opensource-apps/friendlyeats.tar.gz
 third_party/opensource-apps/iosched