To make thinks shiny and cool, add a landing page instead of using the
Sphinx index page.

Signed-off-by: Pablo Galindo <pablogsal@gmail.com>

This was preenting us to get the required checks in PRs only when docs
are updated.

Signed-off-by: Pablo Galindo <pablogsal@gmail.com>

In the latest iteration of the arch Linux container, we need to also
deactivate seccomp to be able to run `gcore` and `ptrace` in the
container.

In addition to that, seems that the new libc is too optimized and some
of our tests are too strict over the number of native frames that must
be present in pthread-based threads, so we need to be a bit more
permissive.

Signed-off-by: Pablo Galindo <pablogsal@gmail.com>