dbus-cpp: not available on musl

Fixes:
http://autobuild.buildroot.net/results/9b2/9b29ff3aac5cd543dbe2a1a632b61e27ca25085e/
http://autobuild.buildroot.net/results/304/3041ed6d7ff648f805cf2e29762e2b57cd0540e4/

musl doesn't provide the initializer for recursive pthread mutexes.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/dbus-cpp/Config.in

@@ -4,6 +4,7 @@ config BR2_PACKAGE_DBUS_CPP
 	depends on BR2_TOOLCHAIN_HAS_THREADS # dbus
 	depends on BR2_USE_MMU # dbus
 	depends on BR2_INSTALL_LIBSTDCPP
+	depends on !BR2_TOOLCHAIN_USES_MUSL # no PTHREAD_RECURSIVE_MUTEX_*
 	select BR2_PACKAGE_EXPAT
 	help
 	  dbus-c++ attempts to provide a C++ API for D-BUS.
@@ -12,7 +13,8 @@ config BR2_PACKAGE_DBUS_CPP
 
 	  http://sourceforge.net/projects/dbus-cplusplus/
 
-comment "dbus-c++ needs a toolchain w/ C++, threads"
+comment "dbus-c++ needs a uClibc or (e)glibc toolchain w/ C++, threads"
 	depends on BR2_USE_MMU
 	depends on BR2_PACKAGE_DBUS
-	depends on !BR2_INSTALL_LIBSTDCPP || !BR2_TOOLCHAIN_HAS_THREADS
+	depends on !BR2_INSTALL_LIBSTDCPP || !BR2_TOOLCHAIN_HAS_THREADS \
+		|| BR2_TOOLCHAIN_USES_MUSL