Ignore IntelliJ Gradle build outputs

Author: kennknowles

.gitignore

@@ -44,6 +44,7 @@ sdks/python/apache_beam/portability/common_urns.py
 **/*.iml
 **/*.ipr
 **/*.iws
+**/out/**/*
 
 # Ignore Eclipse files.
 **/.classpath

assembly.xml

@@ -69,6 +69,7 @@
                 <exclude>**/.gogradle/**</exclude>
                 <exclude>**/build/**</exclude>
                 <exclude>**/vendor/**</exclude>
+                <exclude>**/out/**</exclude>
                 <exclude>**/.gradletasknamecache</exclude>
 
                 <!-- files generated by the Maven build process. -->

build.gradle

@@ -242,6 +242,7 @@ rat {
     "**/*.iml",
     "**/*.ipr",
     "**/*.iws",
+    "**/out/**/*",
 
     // .gitignore: Ignore Eclipse files.
     "**/.classpath",