Enable adding Ubuntu toolchain PPA by default

[Flamefire]

The default in Boost.CI will be false but some jobs still rely on this, so keep it for now the default.

[jofaber]

Hi Flamefire,
sorry I am hesitating to merge this PR since all jobs in the CI are failing.
Could you provide some Information on what to do here or why it is ok to merge?
Thank you

[Flamefire]

This PR is just a minimal fix to avoid failures in old/existing workflows when we switch the default in Boost.CI

The failing jobs are all on Github Actions but this only changes the drone config. So the failures are unrelated. They look like the coincided with the removal of Boost.StaticAssert, so I synced the branch.
On that topic: See if you want to switch to the reusable workflow: https://github.com/boostorg/boost-ci/blob/master/.github/workflows/ci.yml
This way you benefit from automatic updates to compilers, OS-images etc.
From a quick glance what would be missing is the multitude of multi-arch builds you have now (for all GCC jobs). Boost.CI there has only 1 such job for the coverage job and a few for Windows. Not sure if 32-bit builds for Linux matter enough to add some. If so let me know.

From what I can tell Drone CI doesn't seam to be activated. At least I don't see any Drone jobs at all.
You should check why that is and either fix it or remove the drone config. You could also update it from Boost.CI which has a lot more configs (now).