Add using of a build folder in the INSTALL.md #297

Job	Run time
build (ubuntu-latest, ci-dev-client-only-qt5, 5.15)	3m 55s
build (ubuntu-latest, ci-dev-client-only-qt6, 6.5.*, qtshadertools qtscxml)	5m 6s
build (ubuntu-latest, ci-dev-client-and-ui-qt5, 5.15)	6m 4s
build (ubuntu-latest, ci-dev-client-and-ui-qt6, 6.5.*)	7m 37s
build (windows-latest, ci-dev-client-only-qt5, 5.15)	4m 29s
build (windows-latest, ci-dev-client-only-qt6, 6.5.*, qtshadertools qtscxml)	6m 16s
build (windows-latest, ci-dev-client-and-ui-qt5, 5.15)	7m 44s
build (windows-latest, ci-dev-client-and-ui-qt6, 6.5.*)	9m 51s
build (macos-latest, ci-dev-client-only-qt5, 5.15)	3m 31s
build (macos-latest, ci-dev-client-only-qt6, 6.5.*, qtshadertools qtscxml)	5m 4s
build (macos-latest, ci-dev-client-and-ui-qt5, 5.15)	6m 40s
build (macos-latest, ci-dev-client-and-ui-qt6, 6.5.*)	10m 45s
	1h 17m 2s

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