Update support for .note.gnu.property sections.

The original patch did not give the target enough hooks to discover that
an input object file does not have a particular property. For the
GNU_PROPERTY_X86_FEATURE_1_AND property, for example, where a missing
property should be assumed to be all zeroes, and ANDed with other
object modules, this is essential. We now store the target-specific
properties locally in the Target structure as native uint32_t fields,
then AND the per-object feature bits with the program's feature bits
when we're finished processing each input object file. The target-specific
properties are then added back to the output note section during
finalization.

gold/
	PR gold/22914
	* layout.cc (read_sized_value): Fix spelling of section name.
	(Layout::layout_gnu_property): Call Sized_target::record_gnu_property
	for target-specific properties;
	don't store them with target-independent properties yet.
	(Layout::merge_gnu_properties): New method.
	(Layout::add_gnu_property): New method.
	(Layout::create_gnu_properties_note): Call target to finalize
	target-specific properties. Fix spelling of output section name.
	* layout.h (Layout::merge_gnu_properties): New method.
	(Layout::add_gnu_property): New method.
	* object.cc (Sized_relobj_file::do_layout): Call
	Layout::merge_gnu_properties.
	* target.h (Target::merge_gnu_property): Remove.
	(Target::finalize_gnu_properties): New method.
	(Target::do_merge_gnu_property): Move to Sized_target and rename.
	(Target::do_finalize_gnu_properties): New virtual method.
	(Sized_target::record_gnu_property): Moved and renamed from
	Target::do_merge_gnu_property.
	(Sized_target::merge_gnu_properties): New virtual method.
	* x86_64.cc (Target_x86_64::isa_1_used_, isa_1_needed_)
	(feature_1_, object_feature_1_, seen_first_object_): New data members.
	(Target_x86_64::do_merge_gnu_property): Rename to ...
	(Target_x86_64::record_gnu_property): ... this.  Save target-specific
	properties in Target class object.
	(Target_x86_64::merge_gnu_properties): New method.
	(add_property): New static inline function.
	(Target_x86_64::do_finalize_gnu_properties): New method.
	* testsuite/Makefile.am (gnu_property_test): Remove C source file;
	link directly without compiler driver.
	* testsuite/Makefile.in: Regenerate.
	* testsuite/gnu_property_a.S: Add _start.