Prevent include path clashes from system installs of dlib as well as suppress

warning messages from boost and python system header files.

dlib/cmake_utils/add_python_module

@@ -118,12 +118,6 @@ endif()
 
 
 
-INCLUDE_DIRECTORIES("${Boost_INCLUDE_DIRS}")
-if (PYTHON_INCLUDE_PATH)
-   INCLUDE_DIRECTORIES("${PYTHON_INCLUDE_PATH}" )
-else()
-   INCLUDE_DIRECTORIES("${PYTHON_INCLUDE_DIRS}" )
-endif()
 
 message(STATUS "USING BOOST_LIBS: ${Boost_LIBRARIES}")
 if (WIN32)
@@ -152,6 +146,14 @@ macro(add_python_module module_name module_sources )
    ADD_LIBRARY(${module_name}_ SHARED ${module_sources} ${ARGN} )
    TARGET_LINK_LIBRARIES(${module_name}_ ${Boost_LIBRARIES} dlib::dlib)
 
+    target_include_directories(${module_name}_ SYSTEM PUBLIC "${Boost_INCLUDE_DIRS}")
+    if (PYTHON_INCLUDE_PATH)
+        target_include_directories(${module_name}_ SYSTEM PUBLIC "${PYTHON_INCLUDE_PATH}" )
+    else()
+        target_include_directories(${module_name}_ SYSTEM PUBLIC "${PYTHON_INCLUDE_DIRS}" )
+    endif()
+
+
    if(WIN32 AND NOT CYGWIN)
       TARGET_LINK_LIBRARIES(${module_name}_ ${PYTHON_LIBRARIES})
       SET_TARGET_PROPERTIES( ${module_name}_