The run and start goals have a deprecated <jvm-args/> configuration object. The replacement is <java-opts/> which is an array and named more inline with what WildFly uses for it's environment variable.

Note that the <jvm-args/> was simply a space delimited listing of JVM options. However this can still be done in the <java-opts/> as the goals have a setter method which accepts a String and creates an array based on the space delimited arguments.