cookbook: only checkout the master branch.

The master branch is the default stable branch of the project.
Users are free to check out other dev branches afterwards.

Signed-off-by: Emmanuel Roullit <emmanuel.roullit@gmail.com>
cookbook: install clang to dev environment.

Signed-off-by: Emmanuel Roullit <emmanuel.roullit@gmail.com>
apt: track apt cookbook v2.0.0

Signed-off-by: Emmanuel Roullit <emmanuel.roullit@gmail.com>