[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 #4 from Tom de Vries <vries at gcc dot gnu.org> ---
Created attachment 44957
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=44957&action=edit
WIP patch, follows .gnu_debugaltlink