Add __attribute__ to declaration.

tests/cksum_write.c

@@ -34,6 +34,13 @@ parse_intarg(const char msg[])
   return (int)temp;
 }
 
+/* If we're not using GNU C, elide __attribute__ */
+#if ! defined __GNUC__ && ! defined __attribute__
+#  define  __attribute__(x)  /*NOTHING*/
+#endif
+static void
+allocError(const char *msg) __attribute__((noreturn));
+
 static void
 allocError(const char *msg)
 {