* configure.ac (target_configdirs): Substitute.
	* Makefile.def: Bootstrap target module libgomp.
	Add dependency of all-target-libstdc++-v3 on configure-target-libgomp.
	* Makefile.tpl (TARGET_CONFIGDIRS): New makefile variable.
	(BASE_TARGET_EXPORTS): Export TARGET_CONFIGDIRS.
	* configure, Makefile.in: Regenerate.