I think I had to increase both, the MAVEN_OPTS and the extraJvmArgs,
to get this working.
As I understood it, it's like that:
when you call
>mvn XXX
then the mvn process gets the amount of memory specified in MAVEN_OPTS
from the OS.
let's say: 256MB
then this process will fork a java-process (to do the gwt-
complilation) and this jvm-process tries to allocate the amount of
memory specified in extraJvmArgs.
but I think, that the OS does not allow the forked process to request
more data than the current process's limit (of 256MB)
thus setting extraJvmArgs to a higher level than specified in
MAVEN_OPTS has no effect
please note, that I am absolutely not sure about this and it might
also depend on the OS an settings, etc.
Anyone please correct me if this is wrong.