cmake: use CMake standard convention for Octomap

CMakeLists.txt

@@ -85,7 +85,7 @@ endif ()
 
 search_for_boost()
 # Optional dependencies
-add_optional_dependency("octomap >= 1.6")
+ADD_PROJECT_DEPENDENCY(octomap PKG_CONFIG_REQUIRES "octomap >= 1.6")
 if (OCTOMAP_FOUND)
   SET(HPP_FCL_HAVE_OCTOMAP TRUE)
   string(REPLACE "." ";" VERSION_LIST ${OCTOMAP_VERSION})

src/CMakeLists.txt

@@ -193,8 +193,9 @@ else()
   message(STATUS "Assimp version does not have unified headers")
 endif()
 IF(OCTOMAP_FOUND)
-  PKG_CONFIG_USE_DEPENDENCY(${LIBRARY_NAME} octomap)
-  target_compile_definitions (${LIBRARY_NAME} PUBLIC
+  target_include_directories(${LIBRARY_NAME} SYSTEM PUBLIC ${OCTOMAP_INCLUDE_DIR})
+  target_link_libraries(${LIBRARY_NAME} PUBLIC ${OCTOMAP_LIBRARY})
+  target_compile_definitions (${LIBRARY_NAME} PRIVATE
     -DHPP_FCL_HAVE_OCTOMAP
     -DOCTOMAP_MAJOR_VERSION=${OCTOMAP_MAJOR_VERSION}
     -DOCTOMAP_MINOR_VERSION=${OCTOMAP_MINOR_VERSION}