Use `expose_as` to link to the HTML report, and also attach the xml as a
cobertura artifact

Turns out I need to generate even more boilerplate than just this, so
just write a shitty python script (inspired by RADV/mesa) to do the job.

Makes python part of the build dependency of libplacebo, but meson
already depends on python so nothing has changed.

The CI URL for aarch64 needs to be updated to pull in python3-mako.

In doing so I finally hit the time bomb caused by assuming blacklisting
compute is only needed on that specific driver version. Turns out, the
same issue is present even on newer driver versions. Since I have no
idea how else to work around and/or debug it, just permanently disable
compute on the CI.

Unfortunately, for some reason, the `shaderc` version in this version of
the CI image hits random internal exceptions when trying to compile
pretty much anything. But using glslang directly works. Except for msan,
because we don't have msan-instrumented libc++.

Some other changes needed for whatever reason.

It's difficult to get rid of this one with the usual trick of just
forcibly allocating everything in our stack, since the actual struct is
stack-allocated by the vulkan driver.

Do the sensible thing and just #ifndef MSAN

coverage-text is rounded to whole percentages for some reason.

I put it here because this one doesn't actually execute the tests. Just
make sure it compiles (and that clang doesn't complain about it)

Oops. Maybe I should have used the `ci` branch to test my changes. If
only pushing to that branch didn't spam the IRC...

We're surprisingly close to the 30s timeout for llvmpipe/swrast

The GPU CI instance still hangs inside the new environment for some
reason, but the main buildbots can handle it fine.

So we can actually test these at runtime with a GPU

I don't remember what this disabling was about, but it should hopefully
no longer be needed.

We have a new image for these, now.

Reverts 7c6b74ad

Blocked by upstream aarch64 images failing to compile. Will be reverted
as soon as they work again.

cf. https://code.videolan.org/videolan/docker-images-aarch64/pipelines

This makes the GPU CI stuff actually work. Finally, coverage \o/

All hail the cloud overlords and their VMs with GPUs

The image now correctly runs `ldconfig` so we no longer need
LD_LIBRARY_PATH