Explain yarn.version in Maven build docs

docs/building-with-maven.md

@@ -37,13 +37,13 @@ For Apache Hadoop versions 1.x, Cloudera CDH MRv1, and other Hadoop versions wit
     # Cloudera CDH 4.2.0 with MapReduce v1
     $ mvn -Dhadoop.version=2.0.0-mr1-cdh4.2.0 -DskipTests clean package
 
-For Apache Hadoop 2.x, 0.23.x, Cloudera CDH MRv2, and other Hadoop versions with YARN, you should also enable the "hadoop2-yarn" profile:
+For Apache Hadoop 2.x, 0.23.x, Cloudera CDH MRv2, and other Hadoop versions with YARN, you should enable the "hadoop2-yarn" profile and set the "yarn.version" property:
 
     # Apache Hadoop 2.0.5-alpha
-    $ mvn -Phadoop2-yarn -Dhadoop.version=2.0.5-alpha -DskipTests clean package
+    $ mvn -Phadoop2-yarn -Dhadoop.version=2.0.5-alpha -Pyarn.version=2.0.5-alpha -DskipTests clean package
 
     # Cloudera CDH 4.2.0 with MapReduce v2
-    $ mvn -Phadoop2-yarn -Dhadoop.version=2.0.0-cdh4.2.0 -DskipTests clean package
+    $ mvn -Phadoop2-yarn -Dhadoop.version=2.0.0-cdh4.2.0 -Pyarn.version=2.0.0-chd4.2.0 -DskipTests clean package
 
 
 ## Spark Tests in Maven ##