ci: Don't install Qt when running on self-hosted #41

Job	Run time
build (ubuntu-24.04, ci-release-static-qt5, 5.15)	3m 21s
build (ubuntu-24.04, ci-dev-static-qt5, 5.15)	26m 41s
build (ubuntu-24.04, ci-python-qt6, 6.6.0)	4m 19s
build (ubuntu-24.04, ci-release-static-qt6, 6.3.*)	3m 38s
build (ubuntu-24.04, ci-dev-static-qt6, 6.3.*)	7m 12s
build (windows-2022, ci-release-static-qt5, 5.15)	4m 10s
build (windows-2022, ci-dev-static-qt5, 5.15)	5m 25s
build (windows-2022, ci-python-qt6, 6.6.0)	1m 18s
build (windows-2022, ci-release-static-qt6, 6.3.*)	4m 11s
build (windows-2022, ci-dev-static-qt6, 6.3.*)	6m 42s
build (windows-2019, ci-release-static-qt5, 5.15)	4m 1s
build (windows-2019, ci-dev-static-qt5, 5.15)	4m 51s
build (windows-2019, ci-python-qt6, 6.6.0)	5m 3s
build (windows-2019, ci-release-static-qt6, 6.3.*)	4m 55s
build (windows-2019, ci-dev-static-qt6, 6.3.*)	5m 54s
build (macos-13, ci-release-static-qt5, 5.15)	3m 26s
build (macos-13, ci-dev-static-qt5, 5.15)	4m 17s
build (macos-13, ci-python-qt6, 6.6.0)	6m 31s
build (macos-13, ci-release-static-qt6, 6.3.*)	4m 0s
build (macos-13, ci-dev-static-qt6, 6.3.*)	8m 0s
build (ubuntu-24.04, ci-clang-tidy-qt6, 6.3.*)	23m 5s
build (ubuntu-24.04, clazy, --preset=clazy, 5.15)	3m 29s
build (ubuntu-24.04, ci-dev-valgrind-qt5, 5.15)	24m 4s
build (ubuntu-24.04, ci-dev-valgrind-qt6, 6.5.*)	24m 15s
	3h 12m 48s

Provide feedback