You can only use CompileStatic if you limit the plugin to Grails 2.2+ since older apps will have pre-2.0 versions of Groovy
You need to export the spymemcached to compile all of the plugin source. Even if it was just a runtime dependency, you would still need to export it because BuildConfig.groovy is only used at plugin build time to create plugin.xml and the POM files. Client apps resolve dependencies using the POM, not BuildConfig
cleanup