Add an Ant build rule

In order to avoid having to check out a large portion of the Android
framework, allow Volley to be self-contained (and built using the
existing Android application build system).

Change-Id: I45a23b98a2008ad707532da31f1e9b75c7071c25
diff --git a/custom_rules.xml b/custom_rules.xml
new file mode 100644
index 0000000..1b94e5d
--- /dev/null
+++ b/custom_rules.xml
@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project name="volley-rules" default="help">
+
+  <!-- A rule to generate the JAR for inclusion in an Android
+       application. Output file will be bin/volley.jar -->
+  <target name="jar" depends="-compile">
+    <jar destfile="bin/volley.jar"
+         basedir="bin/classes" />
+  </target>
+</project>