PR debug/86964
	* dwarf2out.c (premark_used_variables): New function.
	(prune_unused_types_walk): Do not mark not premarked external
	variables.
	(prune_unused_types): Call premark_used_variables.

	* gcc.dg/debug/dwarf2/pr86964.c: New testcase.

From-SVN: r269925