Fails to build:
/usr/pkg/java/openjdk11/bin/java -Xmx256m -jar /usr/pkg/share/java/classes/antlr.jar -make -Xmultithreaded -Xconversiontimeout 10000 -fo . ./belle_sip_message.g
no main manifest attribute, in /usr/pkg/share/java/classes/antlr.jar