fixed downstream python cmake not found (#1063)

CMakeLists.txt

@@ -1029,6 +1029,9 @@ IF(NOT TORCH_FOUND)
 ENDIF()
 IF(NOT WITH_PYTHON OR NOT Python3_FOUND)
    SET(PYTHON "//")
+   SET(CONF_WITH_PYTHON 0)
+ELSE()
+   SET(CONF_WITH_PYTHON 1)
 ENDIF()
 IF(ADD_VTK_GUI_SUPPORT_QT_TO_CONF)
    SET(CONF_VTK_QT true)

RTABMapConfig.cmake.in

@@ -50,6 +50,10 @@ IF(@CONF_WITH_OCTOMAP@)
   find_dependency(octomap)
 ENDIF()
 
+IF(@CONF_WITH_PYTHON@)
+  find_dependency(Python3 COMPONENTS Interpreter Development NumPy)
+ENDIF()
+
 # Provide those for backward compatibilities (e.g., catkin requires them to propagate dependencies)
 set(RTABMap_INCLUDE_DIRS "")
 set(RTABMap_LIBRARIES "")