libtool: Unset CXX. It is not needed to build libtool, but if set configure...

libtool: Unset CXX. It is not needed to build libtool, but if set configure preferes CXX over CC to build the global_symbol_pipe test program. So if there is no c++ compiler or the c++ installation is broken we end up with a broken libtool script. Fixes #5022

SVN-Revision: 16212

package/libtool/Makefile

@@ -25,6 +25,7 @@ include $(INCLUDE_DIR)/host-build.mk
 include $(INCLUDE_DIR)/package.mk
 
 CONFIGURE_PREFIX=$(STAGING_DIR)/host
+CONFIGURE_VARS+= CXX=no
 export GLOBAL_LIBDIR=$(STAGING_DIR)/usr/lib
 
 define Package/libltdl