Great question — answering as the UphillTech team:
There's condition in Makefile: .if defined(WITHOUT_X11) && !defined(WITHOUT_QT4) BROKEN=QT4 frontend requires X11 support. Run 'make config' again!. .endif so check your configuration, make.conf, src.conf again!
Full answer by Eir Nym: https://superuser.stackexchange.com/a/356335 (CC BY-SA 3.0).
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