CMake: make install work using installed VTK version (fix)

Author: codeling

cmake/Common.cmake

@@ -324,12 +324,16 @@ if ("IOOggTheora" IN_LIST VTK_AVAILABLE_COMPONENTS)
 endif()
 find_package(VTK COMPONENTS ${VTK_COMPONENTS})
 if (MSVC)
+	# TODO: avoid duplication between here and folder for Visual studio running environment path
 	if (EXISTS "${VTK_DIR}/bin/Release")
 		set(VTK_LIB_DIR "${VTK_DIR}/bin/Release")
-	elseif (EXISTS "${VTK_DIR}/bin")
-		set(VTK_LIB_DIR "${VTK_DIR}/bin")
 	else()
-		message(SEND_ERROR "Did not find a VTK dll folder in ${VTK_DIR}!")
+		# when using an installed VTK version, we only know the relative path from the vtk-config.cmake file
+		# we are not aware of a variable containing the "base folder" of the VTK installation
+		get_filename_component(VTK_LIB_DIR "../../../bin" REALPATH BASE_DIR "${VTK_DIR}")
+		if (NOT EXISTS "${VTK_LIB_DIR}")
+			message(SEND_ERROR "Did not find a VTK dll folder (checked: ${VTK_DIR}/bin/Release, ${VTK_LIB_DIR})!")
+		endif()
 	endif()
 else()
 	if (EXISTS "${VTK_DIR}/lib")