This removes the DW_TAG_imported_unit we generate for each referenced
early debug unit in LTRANS units.  They are more harmful than they
do good and the semantics can be read in a way making it even wrong.

2020-04-02  Richard Biener  <rguenther@suse.de>

	PR debug/94450
	* dwarf2out.c (dwarf2out_early_finish): Remove code emitting
	DW_TAG_imported_unit.