OF-617: When property 'halt.on.plugin.error' is set, then build should fail when a plugin fails.

git-svn-id: http://svn.igniterealtime.org/svn/repos/openfire/trunk@13472 b35dd754-fafc-0310-a699-88a17e54d16e

build/build.xml

@@ -1622,6 +1622,7 @@
                     <property name="exception" refid="exception_ref" />
                     <property name="message" value="Error building plugin: @{plugin}. Exception:${line.separator}${exception}" />
                     <echo message="${message}" />
+                    <fail if="halt.on.plugin.error" message="${message}" />
                 </catch>
             </trycatch>
         </sequential>