Avoid downloading files inside Docker

I am trying to generate a config for debian:buster, and get this error message:
```
ERROR: Analysis of target '//java/com/engflow/example:example' failed; build aborted: com.google.devtools.build.lib.packages.RepositoryFetchException: no such package '@rbe_default//config': Traceback (most recent call last):

+ /rbe_autoconf/bazelisk build @local_config_cc//...
2020/04/14 14:04:00 Downloading https://releases.bazel.build/2.2.0/release/bazel-2.2.0-linux-x86_64...
2020/04/14 14:04:00 could not download Bazel: HTTP GET https://releases.bazel.build/2.2.0/release/bazel-2.2.0-linux-x86_64 failed: Get https://releases.bazel.build/2.2.0/release/bazel-2.2.0-linux-x86_64: x509: certificate signed by unknown authority
+ echo 'Could not create outputs_tar, see docker log for details:'
++ /usr/bin/docker logs 514b11ea9ede385a0f687903c34d2e55ac0879c4f071647e83bc1e292c9162fc
```

My hypothesis is that debian buster doesn't come with the right set of certificates to connect to releases.bazel.build. However, I am not sure why that should be a requirement - it seems like it should be possible to create a config by downloading the bazel binary outside of the container and copying it in to generate the config.

Reproduce config generation with debian:buster and inspect the `/rbe_autoconf/bazelisk` invocation and Docker logs shown in the report. Trace where the Bazel binary is obtained, then define completion as generating the config without downloading files from inside the container.

Written by the indexing model from the issue text.