Update metalava to build & run with 3.2.0-alpha16

Change-Id: I153d1abda7e4192714cf72ffddb2334262097d22
diff --git a/.gitignore b/.gitignore
index fffd916..dd93b08 100644
--- a/.gitignore
+++ b/.gitignore
@@ -5,5 +5,6 @@
 /.idea/workspace.xml
 /.idea/runConfigurations
 /out
+build/
 stub-annotations/out
 .DS_Store