configure: error: Package requirements (appstream >= 0.12.0) were not met:
Package 'appstream', required by 'virtual:world', not found
Consider adjusting the PKG_CONFIG_PATH environment variable if you
installed software in a non-standard prefix.
Alternatively, you may set the environment variables APPSTREAM_CFLAGS
and APPSTREAM_LIBS to avoid the need to call pkg-config.
See the pkg-config man page for more details.
!!! Please attach the following file when seeking support:
!!! /var/tmp/portage/sys-apps/flatpak-1.14.0/work/flatpak-1.14.0/config.log
 * ERROR: sys-apps/flatpak-1.14.0::core-kit failed (configure phase):
 *   econf failed
 *
 * Call stack:
 *               ebuild.sh, line   93:  Called src_configure
 *             environment, line 3863:  Called econf '--enable-sandboxed-triggers' '--enable-xauth' '--localstatedir=/var' '--without-system-bubblewrap' '--without-system-dbus-proxy' '--disable-documentation' '--disable-gtk-doc' '--enable-introspection' '--enable-system-helper' '--disable-seccomp' '--without-systemd'
 *        phase-helpers.sh, line  680:  Called __helpers_die 'econf failed'
 *   isolated-functions.sh, line  112:  Called die
 * The specific snippet of code:
 *               die "$@"
 *
 * If you need support, post the output of `emerge --info '=sys-apps/flatpak-1.14.0::core-kit'`,
 * the complete build log and the output of `emerge -pqv '=sys-apps/flatpak-1.14.0::core-kit'`.
 * The complete build log is located at '/var/tmp/portage/sys-apps/flatpak-1.14.0/temp/build.log'.
 * The ebuild environment file is located at '/var/tmp/portage/sys-apps/flatpak-1.14.0/temp/environment'.
 * Working directory: '/var/tmp/portage/sys-apps/flatpak-1.14.0/work/flatpak-1.14.0'
 * S: '/var/tmp/portage/sys-apps/flatpak-1.14.0/work/flatpak-1.14.0'
 * Messages for package sys-apps/flatpak-1.14.0:
 * ERROR: sys-apps/flatpak-1.14.0::core-kit failed (configure phase):
 *   econf failed