cmake: Avoid adding default path as system directory for GCC 6.x

ChristofKaufmann · ChristofKaufmann · commit 583e3a68758f · 2017-03-09T16:23:53.000+01:00
This is a completion for PR opencv#7390 and fixes opencv#6517 and opencv#815.
diff --git a/cmake/OpenCVPCHSupport.cmake b/cmake/OpenCVPCHSupport.cmake
@@ -65,6 +65,9 @@ MACRO(_PCH_GET_COMPILE_FLAGS _out_compile_flags)
         ocv_is_opencv_directory(__result ${item})
         if(__result)
           LIST(APPEND ${_out_compile_flags} "${_PCH_include_prefix}\"${item}\"")
+        elseif(CMAKE_COMPILER_IS_GNUCXX AND NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS "6.0" AND
+               item MATCHES "/usr/include$")
+          # workaround for GCC 6.x bug
         else()
           LIST(APPEND ${_out_compile_flags} "${_PCH_isystem_prefix}\"${item}\"")
         endif()
@@ -75,6 +78,9 @@ MACRO(_PCH_GET_COMPILE_FLAGS _out_compile_flags)
         ocv_is_opencv_directory(__result ${item})
         if(__result)
           LIST(APPEND ${_out_compile_flags} "${_PCH_include_prefix}\"${item}\"")
+        elseif(CMAKE_COMPILER_IS_GNUCXX AND NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS "6.0" AND
+               item MATCHES "/usr/include$")
+          # workaround for GCC 6.x bug
         else()
           LIST(APPEND ${_out_compile_flags} "${_PCH_isystem_prefix}\"${item}\"")
         endif()
