sbom-generator creates SPDX documents for installed packages.

Each package installs an SBOM file in the share/sbom/pc directory.
The file uses the pc(5) format.
sbom-generator reads these files.
For each file, it creates two documents:

- An SPDX 2.2 document (.spdx) in the share/sbom/spdx-2.2 directory.
  It uses bomtool.
- An SPDX 3.0.1 document (.jsonld) in the share/sbom/spdx-3.0.1 directory.
  It uses spdxtool.

Each document includes the dependencies of the package.
It also includes the dependencies of each dependency.
