clean up clang case

teensy3/mk20dx128.c

 void startup_late_hook(void)		__attribute__ ((weak, alias("startup_default_late_hook")));
 
 
-#ifdef __clang__
-// Clang seems to generate slightly larger code with Os than gcc
-__attribute__ ((optimize("-Os")))
-#else
-#if defined(__PURE_CODE__) || !defined(__OPTIMIZE__)
+#if defined(__PURE_CODE__) || !defined(__OPTIMIZE__) || defined(__clang__)
 // cases known to compile too large for 0-0x400 memory region
 __attribute__ ((optimize("-Os")))
 #else
 // hopefully all others fit into startup section (below 0x400)
 __attribute__ ((section(".startup"),optimize("-Os")))
 #endif
-#endif
 void ResetHandler(void)
 {
 	uint32_t *src = &_etext;