log4cxx: needs threads

Fixes build failures such as the following.

  http://autobuild.buildroot.net/results/7b73901d9e8b5098cd96b54d292bb3ffffb3fe37/

Signed-off-by: Simon Dawson <spdawson@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
1 file changed