Comment # 8 on bug 1012533 from Tom de Vries

(In reply to Richard Biener from comment #7)
> I think RedHat also keeps some bare debug info to allow pretty backtraces
> in the binaries where compression could reduce the binary size penalty.

I think you're referring to MiniDebugInfo (
https://fedoraproject.org/wiki/Features/MiniDebugInfo ) stored in a section
called .gnu_debugdata.  This is already compressed, not using objcopy though,
but by running xz on the section before adding it using objcopy --add-section.