download.01.org certificate verification failed - CRLfile missing?

You can download the certificate manually with openssl and add it into your local trusted certificates:

echo -n | openssl s_client -connect download.01.org:443 | \
  sed -ne '/-BEGIN CERTIFICATE-/,/-END CERTIFICATE-/p' | \
  sudo tee '/usr/local/share/ca-certificates/download_01_org.crt'
sudo update-ca-certificates

I've sent a message on 01.org contact form concerning this certificate problem and linking to this thread.

We'll see if it's a man in the middle attack, a server misconfiguration or a new parent certificate unknown on client side.

update, I had a response from intel :

Appreciate you letting us know. We are aware of the situation and we are addressing it. We are updating all our infrastructure to IPv6 and that caused this issue.