Check compiler _M_ARM define instead of WINAPI define.

include/bx/platform.h

@@ -109,7 +109,7 @@
 						)
 
 // http://sourceforge.net/apps/mediawiki/predef/index.php?title=Architectures
-#if defined(__arm__) || (defined(WINAPI_FAMILY) && (WINAPI_FAMILY == WINAPI_FAMILY_PHONE_APP))
+#if defined(__arm__) || defined(_M_ARM)
 #	undef BX_CPU_ARM
 #	define BX_CPU_ARM 1
 #	define BX_CACHE_LINE_SIZE 64