tests/docker: use a gcc-10 based image for arm64 tests

As we enable newer features that we want to test on arm64 targets we
need newer compilers. Split off a new debian-arm64-test-cross image
which we can use to build these new tests.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20200520140541.30256-11-alex.bennee@linaro.org>
3 files changed