[Bug libbacktrace/87182] libbacktrace does not use GCC own zlib

[joseph at codesourcery dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87182

--- Comment #3 from joseph at codesourcery dot com <joseph at codesourcery dot com> ---
Host libbacktrace would need to use GCC's host zlib and target 
libbacktrace would need to use GCC's target zlib for the same target 
multilib (which would require appropriate dependencies to be added to 
cause a target zlib to be built; I think it used to be built for GCJ, but 
I don't see any current dependencies that would result in it being built).