Don't try to read a build_id as string in find_alt_debug_info_link.

Don't try to read a build_id as string in find_alt_debug_info_link.

The GCC8 address sanitizer found an issue in find_alt_debug_info_link.
It tried to convert a build-id byte sequence into a string. But the
build-id byte sequence is not a zero terminated sequence of chars.
So it could run off way past the section data.

The code never actually uses the build-id. It could use it to verify
the referenced alt-file is the correct one. But since it uses elfutils
to actually load the alt file it doesn't have to, since elfutils will
already check the build-id matches.

So just remove the build_id argument from find_alt_debug_info_link
and don't try to convert and return it as a string.

	* src/abg-dwarf-reader.cc (find_alt_debug_info_link): Remove
	build_id argument. Don't try to read the buildid chars as a
	string.
	(find_alt_debug_info): Don't call find_alt_debug_info_link
	with a build_id string argument.

Signed-off-by: Mark Wielaard <mark@klomp.org>
Signed-off-by: Dodji Seketeli <dodji@redhat.com>