People doesn't depend on vtk.

people/CMakeLists.txt

@@ -1,10 +1,9 @@
 set(SUBSYS_NAME people)
 set(SUBSYS_DESC "Point cloud people library")
 set(SUBSYS_DEPS common kdtree search sample_consensus filters io visualization geometry segmentation octree)
-set(EXT_DEPS vtk)
 
 PCL_SUBSYS_OPTION(build "${SUBSYS_NAME}" "${SUBSYS_DESC}" ON)
-PCL_SUBSYS_DEPEND(build NAME ${SUBSYS_NAME} DEPS ${SUBSYS_DEPS} EXT_DEPS ${EXT_DEPS})
+PCL_SUBSYS_DEPEND(build NAME ${SUBSYS_NAME} DEPS ${SUBSYS_DEPS})
 
 PCL_ADD_DOC("${SUBSYS_NAME}")
 
@@ -44,8 +43,6 @@ PCL_MAKE_PKGCONFIG(${LIB_NAME} COMPONENT ${SUBSYS_NAME} DESC ${SUBSYS_DESC} PCL_
 PCL_ADD_INCLUDES("${SUBSYS_NAME}" "${SUBSYS_NAME}" ${incs})
 PCL_ADD_INCLUDES("${SUBSYS_NAME}" "${SUBSYS_NAME}/impl" ${impl_incs})
 
-#SET_TARGET_PROPERTIES("${LIB_NAME}" PROPERTIES LINKER_LANGUAGE CXX)
-
 if(WITH_OPENNI)
   PCL_ADD_EXECUTABLE(pcl_ground_based_rgbd_people_detector COMPONENT ${SUBSYS_NAME} SOURCES apps/main_ground_based_people_detection.cpp BUNDLE)
   target_link_libraries(pcl_ground_based_rgbd_people_detector pcl_common pcl_kdtree pcl_search pcl_sample_consensus pcl_filters pcl_io pcl_visualization pcl_segmentation pcl_people)