With the support added in bug 1382564, toolchains can be downloaded
without a tooltool manifest at all, and it's desirable to get rid of
tooltool manifests on jobs that don't need one.
Bug 1374940 adds a MOZ_TOOLCHAINS environment variable with a list of
path@task-id strings, where task-id is corresponding to the (possibly
optimized) toolchain job, and path corresponding to the
toolchain-artifact defined for that toolchain job.
We want to use that to pull artifacts instead of tooltool packages.
The scripts that use tooltool-download.sh don't run regularly, but when
they do, they might hit some download problems (the relengapi proxy
tends to be rather unreliable for some reason), and in that case, it
would be better to retry a few times, like other job types, rather than
fail directly.
All the current users of tooltool-download.sh set $WORKSPACE. This will
allow to reuse the script on different types of workers, that don't have
$WORKSPACE set to $HOME/workspace, but still have the source in
$WORKSPACE/build/src.
Using /home/worker is the build directory has a 30% talos performance
loss, because test machines has a /home mount directory.
MozReview-Commit-ID: zehcGJrUQX
While here, since the tooltool call from the cctools build scripts was
verbose, make the one in tooltool-download.sh verbose. It will benefit
the other things using tooltool-download.sh, making debugging easier
when one needs to look at the tooltool download logs...
