xz: Use ssize_t for the to-be-ignored return value from write(fd, ptr, 1).

It makes no difference here as the return value fits into an int
too and it then gets ignored but this looks better.

src/xz/file_io.c

@@ -140,7 +140,7 @@ io_write_to_user_abort_pipe(void)
 	// handler. So ignore the errors and try to avoid warnings with
 	// GCC and glibc when _FORTIFY_SOURCE=2 is used.
 	uint8_t b = '\0';
-	const int ret = write(user_abort_pipe[1], &b, 1);
+	const ssize_t ret = write(user_abort_pipe[1], &b, 1);
 	(void)ret;
 	return;
 }