PR27100, final link failed: bad value

The failure on this PR is due to using the same bfd section for
multiple output sections.  Commit 21401fc7 managed to create
duplicate linker script output section statements, but not the actual
bfd sections.

	PR 27100
	* ldlang.h (lang_output_section_statement_type): Add dup_output.
	* ldlang.c (lang_output_section_statement_lookup): Set dup_output.
	(init_os): Test dup_output rather than constraint.
	* testsuite/ld-scripts/pr27100.d,
	* testsuite/ld-scripts/pr27100.s,
	* testsuite/ld-scripts/pr27100.t: New test.
	* testsuite/ld-scripts/data.exp: Run it.  Don't exclude aout here.
	* testsuite/ld-scripts/data.d: Do so here instead.
	* testsuite/ld-scripts/fill.d: Likewise.
	* testsuite/ld-scripts/fill16.d: Likewise.