* gnu/packages/qt.scm (qtsvg)[arguments]: Set QT_BUILD_PARTS in the
custom 'configure phase to include tests. Add custom 'set-display
phase to enable offscreen tests.
(qtx11extras, qtxmlpatterns, qtdeclarative, qtwebsockets, qtlocation,
qttools, qtquickcontrols, qtquickcontrols2, qtgraphicaleffects,
qtcharts, qtdatavis3d)[arguments]: Disable tests.
(qtmultimedia)[source]: Edit snippet to not build 'spectrum' example.
[arguments]: Disable tests.
(qtscxml)[source]: Edit snippet to not build 'scion' test.
(qtcanvas3d)[arguments]: Don't build the test suite, don't run the tests.