There doesn't have to be a META-INF/ra.xml if you are using JCA 1.6 + annotations.
However, the packaging is wrong it should be:
acme.rar:
/META-INF/ironjacamar.xml
acme.jar
Including ironjacamar-spec-api-1.0.8-SNAPSHOT.jar and jboss-transaction-api_1.1_spec-1.0.0.Final.jar in the .rar is wrong too.
See http://docs.jboss.org/ironjacamar/userguide/1.0/en-US/html/deployment.html#packagingrequirements