tests/docker: move most cross compilers to buster base

This includes fixing up the dependencies (Which were already wrong for
one of the mips variants).

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20200203090932.19147-2-alex.bennee@linaro.org>
8 files changed