sys-libs/gdbm is required by dev-lang/perl, and as dev-lang/perl presently has: ~ppc-aix ~x64-cygwin sys-libs/gdbm should also.
Unable to check for sanity: > no match for package: sys-libs/gdbm-1.18.1
Unable to check for sanity: > package masked: sys-libs/readline-8.1
All sanity-check issues have been resolved
Unable to check for sanity: > incorrect keywords: ppc-aix
readline: https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=0744aa71b97569b82f51c23fc8164cf31f3d0382 ncurses: https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=9003b0a3fbb2005567c74cdb2cee0ba075baaf1c
x64-cygwin is due removal, it's the only arch left for this bug, hence, closing