Add -gno-strict-dwarf to dg-options in various btf enum tests

The -gno-strict-dwarf option is needed to ensure enum signedness
is added to type_die.

2024-01-22  John David Anglin  <danglin@gcc.gnu.org>

gcc/testsuite/ChangeLog:

	PR debug/113382
	* gcc.dg/debug/btf/btf-bitfields-3.c: Add -gno-strict-dwarf
	option to dg-options.
	* gcc.dg/debug/btf/btf-enum-1.c: Likewise.
	* gcc.dg/debug/btf/btf-enum-small.c: Likewise.
	* gcc.dg/debug/btf/btf-enum64-1.c: Likewise.