How to define a jar filename based on RTC build using Maven?

Generally you can use the finalName element within the build section of the POM to change how generated artifacts are named. Certain plugins also allow setting a finalName that is specific to that plugin's execution; the JAR plugin allows this.

So then your problem becomes how do you make the "rtcbuildname" available within the Maven runtime? Lots of options there, depending on the type of build definition you are using. One approach would be to use the properties:read-project-properties mojo to read the RTC build.properties file.