Substitute clang build link to point to OBS

There a new Open Build Service instance at https://irill8.siege.inria.fr
where we perform Debian Unstable builds whenever a new upload is
accepted. This will be the new clang builder, hence, the distro-tracker
link to clang builds should point there.
3 jobs for clang-builds in 6 minutes and 48 seconds (queued for 2 seconds)
latest
Status Job ID Name Coverage
  Test
passed #37554
flake8

00:03:55

passed #37556
functional-tests

00:06:47

passed #37555
unit-tests

00:04:30

84.0%