This will add ~5m to the build time, but Travis CI SUCK at keeping their tools up to date...

* Add ccache to speed up builds

* Fix circleci config

* fixup! Fix circleci config

* Try again with environment variables

* Set up ccache on MacOS

* Do tests with pytest to run them in parallel

* attempt to handle merge commits better for PR test path

Similar to how we solved this for travis

* Clean up imports

* don't run valgrind if not specified slow_test

* Fix functest after initializer rename

* upload tests results as junit

* Upload test-common files since #200 got merged

* Catch test results upload failure

We're running out of build limits.

This enables address sanitizer and undefined behaviour sanitizer,
but disables leak detection sanitizer.
It seema there is an issue in qemu that we are using, which prevents
spawning leaksanitizer's tracer thread. But as leak detection is
already done by valgrind on x86 build, this functionality is not
absolute need at the moment.

I should be less cocky about pushing these things to master and instead to a PR

clang-format was not flexible enough to allow lining out things on
columns with spaces.

There is an issue with libclang-common-dev [0]

[0]: should be on https://lists.debian.org/debian-powerpc/2019/02/

This has the downside of not supporting running tests on Valgrind, see
the discussion in issue #15. However, this does test quite a lot
already.

This uses the docker container defined in
https://github.com/thomwiggers/debian-unstable-powerpc/.

Co-authored-by: Thom Wiggers <thom@thomwiggers.nl>