when using pcl do not allow it to override compiler flags

cMake/FreeCAD_Helpers/SetupPCL.cmake

@@ -6,6 +6,9 @@ macro(SetupPCL)
     # PCL needs to be found before boost because the PCLConfig also calls find_package(Boost ...),
     # but with different components
     if(FREECAD_USE_PCL)
+        # pcl overrides the compiler flags by adding -Wno-deprecated
+        set (SAVE_CXX_FLAGS ${CMAKE_CXX_FLAGS})
         find_package(PCL REQUIRED COMPONENTS common kdtree features surface io filters segmentation sample_consensus)
+        set (CMAKE_CXX_FLAGS ${SAVE_CXX_FLAGS})
     endif(FREECAD_USE_PCL)
 endmacro(SetupPCL)