Add android_sdk checkout

Bug: chromium:428426
Change-Id: I12c2969fe8b37a604b14300433f3e3f09aeb24e6
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/36584
Reviewed-by: David Benjamin <davidben@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
diff --git a/.gitignore b/.gitignore
index 41e32b9..ce1c300 100644
--- a/.gitignore
+++ b/.gitignore
@@ -7,6 +7,7 @@
 doc/doc.css
 
 util/bot/android_ndk
+util/bot/android_sdk/public
 util/bot/android_tools
 util/bot/cmake-linux64
 util/bot/cmake-linux64.tar.gz