Enhancement: Alpine builds to support multiple architectures

Since OpenWhisk has adopted the AdoptOpenJDK 8 Alpine images as the basis for its core images, I've become interested in making it compatible with not amd64 architectures. The sticking point, it seems, is making glibc, libgcc, and zlib available for ppc64le, aarch64, and s390x architectures. I see two options:

1. Create a dump for tarballs of those libraries. Given their fairly infrequent release schedule this is probably the best option. (This could potentially be automated and brought into the AdoptOpenJDK farm).
2. Use a multi-stage build in the core Dockerfile (yes, I know it's script-generated) to build the libraries as we go.

For the moment, I'm going with approach 1. This issue is for information and tracking purposes.