Include kmod kit in repos

[tjkirch]

Issue number:

Fixes #1275.

Description of changes:

5b032daf Extract kmod kit archive naming to cargo-make variable
e08fdb2f Include kmod kit in repo targets
e157671f BUILDING: update to describe retrieval and use of kmod kit

This allows for easy, safe retrieval of the kmod kit for a given Bottlerocket release. Updating the repo target means we'll automatically upload kits in future releases, starting with v1.0.6.

Note: This is based on #1286 and #1285.

Testing done:

Making a repo now includes the kmod kit:

> cargo make repo
...
23:49:28 [INFO] Writing repo targets to: /home/tjk/work/bottlerocket/build/repos/default/bottlerocket-1.0.5-e08fdb2f/targets
23:49:29 [INFO] Writing repo metadata to: /home/tjk/work/bottlerocket/build/repos/default/bottlerocket-1.0.5-e08fdb2f/aws-k8s-1.17/x86_64
[cargo-make] INFO - Build Done in 6 seconds.

> exa --tree build/repos/default/bottlerocket-1.0.5-e08fdb2f/
build/repos/default/bottlerocket-1.0.5-e08fdb2f
├── aws-k8s-1.17
...
└── targets
...
   ├── d29cee5253a81c8debc701389c1670531c81b2ca6bf478e1900be2d106e4432c.aws-k8s-1.17-x86_64-kmod-kit-v1.0.5.tar.xz -> /home/tjk/work/bottlerocket/build/archives/aws-k8s-1.17-x86_64-kmod-kit-v1.0.5.tar.xz

> grep -A5 kit build/repos/default/bottlerocket-1.0.5-e08fdb2f/aws-k8s-1.17/x86_64/*targets.json
      "aws-k8s-1.17-x86_64-kmod-kit-v1.0.5.tar.xz": {
        "length": 63348696,
        "hashes": {
          "sha256": "d29cee5253a81c8debc701389c1670531c81b2ca6bf478e1900be2d106e4432c"
        }
      },

I synced the repo to an S3 bucket and was able to download it with tuftool:

> tuftool download . --target-name aws-k8s-1.17-x86_64-kmod-kit-v1.0.5.tar.xz --root ./roles/default.root.json --metadata-url "https://redacted/aws-k8s-1.17/x86_64/" --targets-url "https://redacted/targets/"
Downloading targets to "."
        -> aws-k8s-1.17-x86_64-kmod-kit-v1.0.5.tar.xz

Kit is as expected:

> tar tf aws-k8s-1.17-x86_64-kmod-kit-v1.0.5.tar.xz | head -n5
aws-k8s-1.17-x86_64-kmod-kit-v1.0.5/
aws-k8s-1.17-x86_64-kmod-kit-v1.0.5/kernel-devel/
aws-k8s-1.17-x86_64-kmod-kit-v1.0.5/kernel-devel/Documentation/
aws-k8s-1.17-x86_64-kmod-kit-v1.0.5/kernel-devel/Documentation/kbuild/
aws-k8s-1.17-x86_64-kmod-kit-v1.0.5/kernel-devel/Documentation/kbuild/Kconfig.select-break
...

Terms of contribution:

By submitting this pull request, I agree that this contribution is dual-licensed under the terms of both the Apache License, version 2.0, and the MIT license.

[tjkirch]

^ This push addresses (most of) @bcressey's concerns above.

[tjkirch]

^ Quick fix for @bcressey's remaining comment, based on an offline suggestion from him.