cmake: ocv_target_include_directories() handle SYSTEM directories

cmake/OpenCVUtils.cmake

@@ -171,29 +171,55 @@ function(ocv_target_include_directories target)
       ";${ARGN};" MATCHES "/usr/include;")
     return() # workaround for GCC 6.x bug
   endif()
+  set(__params "")
+  set(__system_params "")
+  set(__var_name __params)
   foreach(dir ${ARGN})
+    if("${dir}" STREQUAL "SYSTEM")
+      set(__var_name __system_params)
+    else()
       get_filename_component(__abs_dir "${dir}" ABSOLUTE)
       ocv_is_opencv_directory(__is_opencv_dir "${dir}")
       if(__is_opencv_dir)
-      list(APPEND __params "${__abs_dir}")
+        list(APPEND ${__var_name} "${__abs_dir}")
       else()
-      list(APPEND __params "${dir}")
+        list(APPEND ${__var_name} "${dir}")
+      endif()
     endif()
   endforeach()
   if(HAVE_CUDA OR CMAKE_VERSION VERSION_LESS 2.8.11)
     include_directories(${__params})
+    include_directories(SYSTEM ${__system_params})
   else()
     if(TARGET ${target})
+      if(__params)
         target_include_directories(${target} PRIVATE ${__params})
         if(OPENCV_DEPENDANT_TARGETS_${target})
           foreach(t ${OPENCV_DEPENDANT_TARGETS_${target}})
             target_include_directories(${t} PRIVATE ${__params})
           endforeach()
         endif()
+      endif()
+      if(__system_params)
+        target_include_directories(${target} SYSTEM PRIVATE ${__system_params})
+        if(OPENCV_DEPENDANT_TARGETS_${target})
+          foreach(t ${OPENCV_DEPENDANT_TARGETS_${target}})
+            target_include_directories(${t} SYSTEM PRIVATE ${__system_params})
+          endforeach()
+        endif()
+      endif()
     else()
-      set(__new_inc "${OCV_TARGET_INCLUDE_DIRS_${target}};${__params}")
+      if(__params)
+        set(__new_inc ${OCV_TARGET_INCLUDE_DIRS_${target}})
+        list(APPEND __new_inc ${__params})
         set(OCV_TARGET_INCLUDE_DIRS_${target} "${__new_inc}" CACHE INTERNAL "")
       endif()
+      if(__system_params)
+        set(__new_inc ${OCV_TARGET_INCLUDE_SYSTEM_DIRS_${target}})
+        list(APPEND __new_inc ${__system_params})
+        set(OCV_TARGET_INCLUDE_SYSTEM_DIRS_${target} "${__new_inc}" CACHE INTERNAL "")
+      endif()
+    endif()
   endif()
 endfunction()
 
@@ -1078,6 +1104,16 @@ function(_ocv_append_target_includes target)
     endif()
     unset(OCV_TARGET_INCLUDE_DIRS_${target} CACHE)
   endif()
+
+  if(DEFINED OCV_TARGET_INCLUDE_SYSTEM_DIRS_${target})
+    target_include_directories(${target} SYSTEM PRIVATE ${OCV_TARGET_INCLUDE_SYSTEM_DIRS_${target}})
+    if(OPENCV_DEPENDANT_TARGETS_${target})
+      foreach(t ${OPENCV_DEPENDANT_TARGETS_${target}})
+        target_include_directories(${t} SYSTEM PRIVATE ${OCV_TARGET_INCLUDE_SYSTEM_DIRS_${target}})
+      endforeach()
+    endif()
+    unset(OCV_TARGET_INCLUDE_SYSTEM_DIRS_${target} CACHE)
+  endif()
 endfunction()
 
 function(ocv_add_executable target)