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>

package/log4cxx/Config.in

@@ -5,11 +5,13 @@ config BR2_PACKAGE_LOG4CXX
 	# apr really needs shared library support
 	depends on !BR2_PREFER_STATIC_LIB
 	depends on BR2_INSTALL_LIBSTDCPP
+	depends on BR2_TOOLCHAIN_HAS_THREADS
 	help
 	  Apache log4cxx is a logging framework for C++ patterned
 	  after Apache log4j.
 
 	  http://apache.linux-mirror.org/logging/log4cxx/0.10.0
 
-comment "log4cxx needs a toolchain w/ C++"
-	depends on !BR2_INSTALL_LIBSTDCPP
+comment "log4cxx needs a toolchain w/ C++, threads, dynamic library"
+	depends on !BR2_INSTALL_LIBSTDCPP || !BR2_TOOLCHAIN_HAS_THREADS || \
+		BR2_PREFER_STATIC_LIB