string: only include inline-asm if UCLIBC_HAS_STRING_ARCH_OPT

Signed-off-by: Mike Frysinger <vapier@gentoo.org>

include/string.h

@@ -483,7 +483,7 @@ libc_hidden_proto(strlcpy)
 __END_DECLS
 
 
-#ifdef UCLIBC_INTERNAL
+#if defined(UCLIBC_INTERNAL) && defined(__UCLIBC_HAS_STRING_ARCH_OPT__)
 # if defined __i386__
 #  include <../libc/string/i386/string.h>
 # endif