PR debug/90981 Empty .debug_addr crashes -gdwarf-5 -gsplit-dwarf

PR debug/90981 Empty .debug_addr crashes -gdwarf-5 -gsplit-dwarf

Even if there was no, or an empty address list we would try to generate
a header for the .debug_addr section with -gdwarf-5 and -gsplit-dwarf.
The skeleton DIE would also get a (dangling) DW_AT_addr_base in that case.

	PR debug/90981
	* dwarf2out.c (add_top_level_skeleton_die_attrs): Only add
	DW_AT_addr_base if there is actually a .debug_addr section with
	addresses.
	(output_addr_table): Add DWARF5 table header generation here after
	checking there are actually any addresses from...
	(dwarf2out_finish): ...here.
	* testsuite/g++.dg/pr90981.C: New test.

From-SVN: r273008