BUG: Applied patch from bug#4462.

Modules/Platform/gcc.cmake

@@ -6,7 +6,9 @@ IF(CMAKE_COMPILER_IS_GNUCC)
   SET (CMAKE_C_FLAGS_RELWITHDEBINFO_INIT "-O2 -g")
   SET (CMAKE_C_CREATE_PREPROCESSED_SOURCE "<CMAKE_C_COMPILER> <FLAGS> -E <SOURCE> > <PREPROCESSED_SOURCE>")
   SET (CMAKE_C_CREATE_ASSEMBLY_SOURCE "<CMAKE_C_COMPILER> <FLAGS> -S <SOURCE> -o <ASSEMBLY_SOURCE>")
-  SET (CMAKE_INCLUDE_SYSTEM_FLAG_C "-isystem ")
+  IF(NOT APPLE)
+    SET (CMAKE_INCLUDE_SYSTEM_FLAG_C "-isystem ")
+  ENDIF(NOT APPLE)
 ENDIF(CMAKE_COMPILER_IS_GNUCC)
 
 IF(CMAKE_COMPILER_IS_GNUCXX)
@@ -17,6 +19,8 @@ IF(CMAKE_COMPILER_IS_GNUCXX)
   SET (CMAKE_CXX_FLAGS_RELWITHDEBINFO_INIT "-O2 -g")
   SET (CMAKE_CXX_CREATE_PREPROCESSED_SOURCE "<CMAKE_CXX_COMPILER> <FLAGS> -E <SOURCE> > <PREPROCESSED_SOURCE>")
   SET (CMAKE_CXX_CREATE_ASSEMBLY_SOURCE "<CMAKE_CXX_COMPILER> <FLAGS> -S <SOURCE> -o <ASSEMBLY_SOURCE>")
-  SET (CMAKE_INCLUDE_SYSTEM_FLAG_CXX "-isystem ")
+  IF(NOT APPLE)
+    SET (CMAKE_INCLUDE_SYSTEM_FLAG_CXX "-isystem ")
+  ENDIF(NOT APPLE)
 ENDIF(CMAKE_COMPILER_IS_GNUCXX)