error: Package `gcr-ui-3' not found in specified Vala API directories or GObject-Introspection GIR directories Enabling the "vala" USE flag in app-crypt/gcr allows to build the package.
https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=fe8f23448972db0c44017b6d8db2bbd1f9da46a4