Also check M2_HOME envvar - the most commonly used way to specify a maven version on the commandline.

git-svn-id: https://svn.apache.org/repos/asf/maven/shared/trunk@552919 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/src/main/java/org/apache/maven/it/Verifier.java b/src/main/java/org/apache/maven/it/Verifier.java
index 707c42b..4be5bc8 100644
--- a/src/main/java/org/apache/maven/it/Verifier.java
+++ b/src/main/java/org/apache/maven/it/Verifier.java
@@ -822,6 +822,13 @@
         }
         else
         {
+            mavenHome = System.getenv( "M2_HOME" );
+
+            if ( mavenHome != null )
+            {
+                return mavenHome + "/bin/mvn";
+            }
+
             File f = new File( System.getProperty( "user.home" ), "m2/bin/mvn" );
 
             if ( f.exists() )