The latest version of sys-devel/libtool in prefix-tree is sys-devel/libtool-2.4-r4, but there are ebuilds in gx86 that depend on >=sys-devel/libtool-2.4.2-r1, causing installation of those packages to break unless the offending package versions are manually masked.
multilib, expect further b0rkage, esp on non-ppc/x86/amd64 platforms.