If the user tries to run Jenkins on Java 1.4 and earlier, detect that

more gracefully.

changelog.html

@@ -63,6 +63,8 @@ Upcoming changes</a>
   <li class=bug>
     Fixed a bug in LDAP group search based on memberUid
     (<a href="https://github.com/jenkinsci/jenkins/pull/151">pull request #151</a>)
+  <li class=bug>
+    If the user tries to run Jenkins on Java 1.4 and earlier, detect that more gracefully.
   <li class=rfe>
     AJP port is customizable in RPM/OpenSUSE packages
     (<a href="https://github.com/jenkinsci/jenkins/pull/149">pull request #149</a>)

war/pom.xml

@@ -111,7 +111,7 @@ THE SOFTWARE.
                 <mkdir dir="target/generated-resources" />
 
                 <!-- put executable war header -->
-                <resolveArtifact groupId="org.jenkins-ci" artifactId="executable-war" version="1.20" type="jar" property="executable-war.jar" />
+                <resolveArtifact groupId="org.jenkins-ci" artifactId="executable-war" version="1.21" type="jar" property="executable-war.jar" />
                 <unjar src="${executable-war.jar}" dest="target/generated-resources">
                   <patternset>
                     <include name="**/*.class" />