Add gradle wrapper generated files to .gitignore

Change-Id: I9b0fa506b222aaa4febfc50c59bc819c22b723f7
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/196970
Reviewed-by: Jim Blackler <jimblackler@google.com>
Auto-Submit: Alex Benton <bentonian@google.com>
Reviewed-by: dan sinclair <dsinclair@chromium.org>
Commit-Queue: dan sinclair <dsinclair@chromium.org>
diff --git a/tools/android/.gitignore b/tools/android/.gitignore
index 50e7c68..6eeec9f 100644
--- a/tools/android/.gitignore
+++ b/tools/android/.gitignore
@@ -2,3 +2,5 @@
 /gradlew
 /gradlew.bat
 /local.properties
+gradle/wrapper/gradle-wrapper.jar
+gradle/wrapper/gradle-wrapper.properties