[Bug other/82857] libbacktrace: please support binaries stripped with dwz -m (following the .gnu_debugaltlink)

[vries at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82857

--- Comment #3 from Tom de Vries <vries at gcc dot gnu.org> ---
The dwz man shows:
...
      -M NAME --multifile-name NAME
              Specify the name of the common file that should be put into  the 
.gnu_debugaltlink  section  alongside
              with its build ID.  By default dwz puts there the argument of the
-m option.
...

The debugaltlink looks like:
...
$ objdump -s a.out.debug
Contents of section .gnu_debugaltlink:
 0000 636f6d6d 6f6e2e64 65627567 00583730  common.debug.X70
 0010 8a56187b b2abdbbd 93929f3f f623059e  .V.{.......?.#..
 0020 2f                                   /               
...

and given that this is the buildid of common.debug:
...
$ file common.debug 
common.debug: ELF 64-bit LSB relocatable, x86-64, version 1 (SYSV),
BuildID[sha1]=5837308a56187bb2abdbbd93929f3ff623059e2f, with debug_info, not
stripped
...
indeed .gnu_debugaltlink looks like the zero-terminated "common.debug" string
followed by the buildid.