Generate rtc_base/ssl_roots.h

This directory contains a script to generate the content of rtc_base/ssl_roots.h, to update the SSL roots shipped by WebRTC follow this instructions:

1. Download roots.pem from pki.goog or [curl.se][mozilla-cacert]

2. Launch the script:

$ vpython3 tools_webrtc/sslroots/generate_sslroots.py <the pem file>

3. Step 2 should have generated an ssl_roots.h file right next to the pem file.

4. Overwrite rtc_base/ssl_roots.h with the newly generated one.