Upstream bug: https://sourceware.org/bugzilla/show_bug.cgi?id=21861 Basic gist is binutils, when installed as either cross-x86_64-w64-mingw32/binutils or cross-i686-w64-mingw32/binutils will segfault when building sys-devel/zlib with cross-emerge. Upstream has accepted a small, one-liner patch to fix the issue, which doesn't break glibc system (no idea/word on uclibc). I'd like this patch to be added into the gentoo toolchain patch series for binutils.
Was also applied upstream as: https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=commitdiff;h=54387c7fe27848e41a51c1eccc6a24b3d6d3441f Next step is to add it to binutils patchset.
Fixed in sys-devel/binutils-2.29.1