Fix to disable LTO for Clang

The previous code was assuming Apple == Clang.  This change should both
enable LTO when using gcc on Apple and fix Clang when using it on other
platforms.

CMakeLists.txt

@@ -80,7 +80,7 @@ else()
     set(DEBUG_FLAGS "-g3 -O0")
   endif()
   set(RELEASE_FLAGS "-Ofast -DNDEBUG -Wno-unused-variable")
-  if(NOT APPLE)
+  if(NOT CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
     # There is a clang bug that does not allow to compile code that uses AES-NI intrinsics if -flto is enabled
     set(RELEASE_FLAGS "${RELEASE_FLAGS} -flto")
   endif()