erlang: don't build the Java stuff on the host

We don't need the Java stuff, and it causes build failures on certain
machines:

 http://autobuild.buildroot.org/results/99035e89e101c41d5e8b5ef6a025856f4af88ae2/build-end.log



Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>