gen_init_cpio: Ignore fsync() returning EINVAL on pipes

The reproducer:
echo | ./usr/gen_init_cpio /dev/stdin > /dev/null

fsync() on a pipe fd returns -EINVAL, which makes gen_init_cpio fail.
Ignore -EINVAL from fsync().

Fixes: ae18b94 ("gen_init_cpio: support -o <output_file> parameter")
Cc: David Disseldorp <[email protected]>
Cc: Nicolas Schier <[email protected]>
Signed-off-by: Dmitry Safonov <[email protected]>
Reviewed-by: David Disseldorp <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Nathan Chancellor <[email protected]>

Author: 0x7f454c46

usr/gen_init_cpio.c

@@ -112,7 +112,10 @@ static int cpio_trailer(void)
 	    push_pad(padlen(offset, 512)) < 0)
 		return -1;
 
-	return fsync(outfd);
+	if (fsync(outfd) < 0 && errno != EINVAL)
+		return -1;
+
+	return 0;
 }
 
 static int cpio_mkslink(const char *name, const char *target,