How do I tell the war task not to compile my source files, but instead use the class files that Eclipse creates?

I came up with a better solution than the one I started with.

apply plugin: 'java'
apply plugin: 'war'
apply plugin: 'eclipse-wtp'
  configurations {
   passemble
}
  repositories {
   mavenLocal()
   mavenCentral()
}
  dependencies {
   passemble 'org.apache.portals.pluto:pluto-ant-tasks:2.0.3'
}
  sourceSets {
   main {
      java {
         srcDirs "src"
      }
        resources {
         srcDir "src"
      }
   }
}
  eclipse {
  wtp {
    component {
      resource deployPath: '/', sourcePath: '/WebContent', tag: 'defaultRootSource'
      resource deployPath: '/WEB-INF/classes', sourcePath: '/src'
    }
  }
}
  task passemble {
   description = 'Assemble project so that it may be run on Apache Pluto'
     doLast {
      println 'creating taskdef passemble...'
      ant.taskdef(name: 'passemble', classname: 'org.apache.pluto.ant.AssembleTask', classpath: configurations.passemble.asPath)
        println 'creating temporary web.xml file...'
      File tmp = file('web.xml')
      tmp.createNewFile()
        PrintWriter printWriter = new PrintWriter(tmp);
      printWriter.println '<?xml version="1.0" encoding="UTF-8" standalone="no"?>'
      printWriter.println '<!DOCTYPE web-app PUBLIC'
      printWriter.println '
 "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"'
      printWriter.println '
 "http://java.sun.com/dtd/web-app_2_3.dtd">'
      printWriter.println '<web-app id="WebApp_ID">'
      printWriter.println '</web-app>'
      printWriter.close();
        println 'executing task passemble...'
      ant.passemble(
         webxml: 'web.xml',
          portletxml: 'WebContent/WEB-INF/portlet.xml',
          destfile: 'WebContent/WEB-INF/web.xml')
        println 'deleting temporary web.xml file...'
      delete file('web.xml')
   }
}