ci: Don't install Qt when running on self-hosted #39

Job	Run time
build (ubuntu-24.04, ci-release-static-qt5, 5.15)	5m 13s
build (ubuntu-24.04, ci-dev-static-qt5, 5.15)	8m 41s
build (ubuntu-24.04, ci-python-qt6, 6.6.0)	4m 26s
build (ubuntu-24.04, ci-release-static-qt6, 6.3.*)	3m 45s
build (ubuntu-24.04, ci-dev-static-qt6, 6.3.*)	25m 2s
build (windows-2022, ci-release-static-qt5, 5.15)	3m 55s
build (windows-2022, ci-dev-static-qt5, 5.15)	5m 24s
build (windows-2022, ci-python-qt6, 6.6.0)	1m 48s
build (windows-2022, ci-release-static-qt6, 6.3.*)	4m 9s
build (windows-2022, ci-dev-static-qt6, 6.3.*)	6m 5s
build (windows-2019, ci-release-static-qt5, 5.15)	4m 25s
build (windows-2019, ci-dev-static-qt5, 5.15)	4m 42s
build (windows-2019, ci-python-qt6, 6.6.0)	5m 12s
build (windows-2019, ci-release-static-qt6, 6.3.*)	5m 47s
build (windows-2019, ci-dev-static-qt6, 6.3.*)	6m 11s
build (macos-13, ci-release-static-qt5, 5.15)	4m 29s
build (macos-13, ci-dev-static-qt5, 5.15)	5m 20s
build (macos-13, ci-python-qt6, 6.6.0)	7m 20s
build (macos-13, ci-release-static-qt6, 6.3.*)	4m 44s
build (macos-13, ci-dev-static-qt6, 6.3.*)	6m 55s
build (ubuntu-24.04, ci-clang-tidy-qt6, 6.3.*)	23m 45s
build (ubuntu-24.04, clazy, --preset=clazy, 5.15)	3m 21s
build (ubuntu-24.04, ci-dev-valgrind-qt5, 5.15)	23m 56s
build (ubuntu-24.04, ci-dev-valgrind-qt6, 6.5.*)	23m 46s
	3h 18m 21s

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