cmake: update endianness test

CMakeLists.txt

@@ -6,6 +6,16 @@ include (TestBigEndian)
 include(Templates)
 include(Platform)
 
+test_big_endian(is_big_endian)
+if (is_big_endian)
+	message(STATUS "Target is Big Endian")
+	add_compile_definitions(FX_ENDIAN=1)
+else ()
+	message(STATUS "Target is Little Endian")
+	add_compile_definitions(FX_ENDIAN=0)
+endif ()
+
+
 set(CMAKE_C_STANDARD 99)
 set(CMAKE_C_EXTENSIONS OFF)