qtsingleapplication ebuild defaults to Qt5 version and has no qt5 use-flag, while the goldendict-9999 ebuild requires qtsingleapplication[qt5]. Please change that to qt5(+).
The bug has been closed via the following commit(s): https://gitweb.gentoo.org/proj/qt.git/commit/?id=18224055eb9ab49fd40e65161d46d8d9954239a7 commit 18224055eb9ab49fd40e65161d46d8d9954239a7 Author: Michael Palimaka <kensington@gentoo.org> AuthorDate: 2018-03-13 10:59:02 +0000 Commit: Michael Palimaka <kensington@gentoo.org> CommitDate: 2018-03-13 10:59:07 +0000 app-text/goldendict: fix dev-qt/qtsingleapplication USE dependency Closes: https://bugs.gentoo.org/650368 Package-Manager: Portage-2.3.24, Repoman-2.3.6 app-text/goldendict/goldendict-9999.ebuild | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)