ccache requires a newer version of glibc than could be provided with the
Azure workaround. Revert 87c73e5b5d so
that ccache will work.
This may not work with Azure. If that is the case, we will need to
revert ccache to an earlier build.
Also modifies a comment. This is all to make it more readable, and also
force Docker to give the container new commit tags and rebuild it, since
the root certificates have expired.
This opts to not install the yuzu dependencies from Conan, since this
happens again at build time regardless of installing them here.
Also prevents removing the /tmp directory, to not break building
packages later.
Also use ownstuff ffmpeg, instead of the dead link from mingw-setup.sh
mingw-setup.sh was thus removed as it only did one thing that could be
reduced to a single command in the Dockerfile.
