This currently removes around 25s from compilation time while also being
more resilient to network outages. The drawback is that when changing
the compiler we may need to clean the caches.
In order to use the container infrastructure we can't use sudo to
install packages. Now Travis has a way to install packages by specifying
them in the .travis.yml. This greatly simplifies how we install the
packages and there's no need for a separate script anymore.
This also removes several outdated packages that aren't needed anymore.
This way we can group together the builds that are fast so we pay the
"setup price" just once. Let the long PX4 build on its own VM because
it's the one that takes most of the time building NuttX.
By grouping the projects by target it's also easier to split the build
in more VMs if we want to speed up the build.
Travis build is timing out because it's taking too much time. Let's
split the build so 1) they can run concurrently and 2) we don't timeout.
We still lose some time due to multiple checkouts, but at least we don't
fail the build due to timeout.
Julien BERAUD
Lucas De Marchi
Andrew Tridgell
Jonathan Challinger
Markus Koetter
Arthur Benemann