Fixed tkinter in Alpine

[radarhere]

I was unable to use tkinter with Alpine.

Taking a look at

docker-images/docker/Dockerfile-alpine3.15-x86_64

Line 1 in 6f27449

# based on https://github.com/docker-library/python/blob/8d48af512dc58e9c29c9d4ee59477c195a29cbdc/3.10/alpine3.13/Dockerfile

I found that the docker-library version worked. Comparing the differences, and looking at docker-library/python#484, I've come up with this PR.

This is sort of take two at #30, since it also fixes the problem importing ctypes.

[mattip]

Thanks. /usr/local does seem like a better place to look for the libraries. Does pkg-config work to solve the ambiguity?

When I set this up, there was no option to test wheels conveniently in a different docker than the manylinux* ones they were built in. Is that hypothesis still true? Maybe we should recommend that multibuild users test their wheels on the github actions runners with the setup-python action instead.

[radarhere]

As to whether a library should come from /usr or /usr/local? I don't know. I've found the commit where /usr/local was removed the first time around - 04d759f

build_multilinux and install_run are different, with build_multilinux defaulting to pypa, and install_run defaulting to here. You added the ability to use a custom DOCKER_TEST_IMAGE - multi-build/multibuild#314.

I think the issue is that the lack of native support in GitHub Actions for other architectures.