build: Fix permission.

* build-aux/config.guess: Chmod +x.
* build-aux/config.sub: Chmod +x.

Downloading the file directly, file permission was changed.

• Fixes-commit: 6d2e0546d50a0d4511fb7167566bfd0058a68f38
• Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>