Why does Grails not recognize BuildStandalone?

问题

I have a Grails app (2.3.6) that uses the Grails Build Standalone plugin.

The myapp/grails-app/conf/BuildConfig.groovy:

plugins {
    runtime ":resources:1.2.7"
    compile 'org.grails.plugins:gson:1.1.4'
    compile ":standalone:1.2.3"
    build ":release:3.0.1"
    runtime ":cached-resources:1.0"
    compile ":cache-headers:1.0.4"
}

When I go to myapp and run grails build-standalone myapp.jar --tomcat I get:

$ grails build-standalone myapp.jar --tomcat
|Loading Grails 2.3.6
|Configuring classpath
|Running pre-compiled script
|Script 'BuildStandalone' not found, did you mean:
    1) InstallDependency
    2) Stats
    3) CreateMultiProjectBuild_
    4) TestApp
    5) InstallPlugin
Please make a selection or enter Q to quit:

What is going on here?

来源：https://stackoverflow.com/questions/25248099/why-does-grails-not-recognize-buildstandalone