[Tails-dev] Please review'n'merge feature/jenkins-compatible…

Hi,

On the way to configure our jenkins auto-builder, I had to patch again the
build-tails script.

This is one commit in the feature/jenkins-compatible-build-script, namely
`5cf1c59c`.

It only changes the default permission of the directory where build
results (artifacts in jenkins' language) are saved. This is needed for our
web server to be able to show the content of these directories.

This has already been merged in experimental so that I was able to test it on
our jenkins instance. Works great!

If you're ok with, please merge in stable, devel and testing, the branches
that at the moment are watched and build by our jenkins.

Thanks!

bert.