dependencies: Reject gcj in BR2_NEEDS_HOST_JAVA check

dependencies: Reject gcj in BR2_NEEDS_HOST_JAVA check

Xbmc uses the Groovy java package to generate API code, for details see
http://wiki.xbmc.org/index.php?title=Codegeneration#How_it_works

Groovy itself is broken when used with gcj:
http://jira.codehaus.org/browse/GROOVY-3701

Xbmc recommends to use another java package instead, like openjdk:
http://forum.xbmc.org/showthread.php?tid=199742

Until we come up with a host package to provide a java setup and
in order to make autobuilder happy let´s reject gcj when we check
for a java installation on the host.

Currently Xbmc is the only package using BR2_NEEDS_HOST_JAVA
so changing the behaviour of dependencies.sh has no side effects.

Fixes
http://autobuild.buildroot.net/results/213/213d7454a1dc68cfb8f4c8d9508f52ebf8e58e33/
http://autobuild.buildroot.net/results/639/639cda872cf36c122cbd6139dd76f6b51ac1864e/
http://autobuild.buildroot.net/results/c9e/c9eb12c95b2939c64590692a82af8d84bbd90956/

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>