dwarf: Generate DIEs for external variables with -g1 [93751]

dwarf: Generate DIEs for external variables with -g1 [93751]

-g1 is described in the manual to generate debug info for functions and
external variables. It does that for older debugging formats but not for
DWARF. This change brings DWARF in line with the rest of the debugging
formats and with the manual.

gcc/ChangeLog
2020-03-17  Alexey Neyman  <stilor@att.net>

	PR debug/93751
	* dwarf2out.c (gen_decl_die): Proceed to generating the DIE if
	the debug level is terse and the declaration is public. Do not
	generate type info.
	(dwarf2out_decl): Same.
	(add_type_attribute): Return immediately if debug level is
	terse.

Signed-off-by: Alexey Neyman <stilor@att.net>