Add support for Maven 3 .cmd files in Windows

(cherry picked from commit f7c0a49b)

core/src/main/java/hudson/tasks/Maven.java

@@ -582,12 +582,20 @@ public class Maven extends Builder {
         }
 
         private File getExeFile(String execName) {
-            if(File.separatorChar=='\\')
-                execName += ".bat";
-
             String m2Home = Util.replaceMacro(getHome(),EnvVars.masterEnvVars);
 
-            return new File(m2Home, "bin/" + execName);
+            if(Functions.isWindows()) {
+                File exeFile = new File(m2Home, "bin/" + execName + ".bat");
+
+                // since Maven 3.3 .bat files are replaced with .cmd
+                if (!exeFile.exists()) {
+                    return new File(m2Home, "bin/" + execName + ".cmd");
+                }
+
+                return exeFile;
+            } else {
+                return new File(m2Home, "bin/" + execName);
+            }
         }
 
         /**