From the ebuild: gen_translation() { lrelease -qt=qt5 ${PN}_${1}.ts eend $? || die "failed to generate $1 translation" } This assumes that lrelease in $PATH is being managed by qtchooser, which we do not guarantee. Instead, it's better to call directly: "$(qt5_get_bindir)"/lrelease ${PN}_${1}.ts Also note that lrelease is provided by dev-qt/linguist-tools but that's a missing dependency (needed only at build time).
Fixed as reviewed over IRC. commit 61dbfd2cdd29094de8ebd2b5bf4d4a5c7ab4b771