sources: switch to empty cargo workspace

[ginglis13]

Issue number:

Closes #7

Description of changes:

Switch from a fake package in sources/ to an empty Cargo workspace. The fake package was added in #4 to appease the build system, which without a sources/ dir complains:

this may be fixable by adding sources to the workspace.members array of the manifest located at: /home/fedora/kernel-kit/Cargo.toml
Alternatively, to keep it out of the workspace, add the package to the workspace.exclude array, or add an empty [workspace] table to the package's manifest.

#4 added a fake package and added it to the top level workspace's exclude array; this PR takes the other option.
This has resolved issues faced in #7

Testing done:

make

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.