Produce release for Z(s390x)

### Description of the problem / feature request:
It would be nice to see releases for other architectures then, x86_64. My ask is to have releases be produced for `s390x`.

### Feature requests: what underlying problem are you trying to solve with this feature?

Building Bazel from source is another layer of complexity since there is no Bazel release for `s390x`. I have to install build tools and compile it each time I want to use it.

### Bugs: what's the simplest, easiest way to reproduce this bug? Please provide a minimal example if possible.

N/A

### What operating system are you running Bazel on?

Ubuntu 18.04 - `s390x`

### What's the output of `bazel info release`?

N/A

### If `bazel info release` returns "development version" or "(@non-git)", tell us how you built Bazel.

N/A

### What's the output of `git remote get-url origin ; git rev-parse master ; git rev-parse HEAD` ?

N/A

### Have you found anything relevant by searching the web?

I search the closed and open issues in this repo and it seems like people are already building it for `s390x` and thus there is an interest in putting out releases.

### Any other information, logs, or outputs that you want to share?

If the Bazel team does not have access to `s390x`, we can change that! Happy to talk more about getting people access once I know if anyone is onboard with supporting this.

No files, tests, or entry points are named in the issue. Start by locating Bazel’s release and architecture-specific build configuration; done means a Bazel release is produced for s390x.

Written by the indexing model from the issue text.