Merge #419

419: Make pci-ids optional r=stlankes a=mkroening

Supersedes https://github.com/hermitcore/libhermit-rs/pull/155

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This reduces size of the resulting hello-world application from 4.13 MB to 1.04 MB if the pci-ids database is not included.

Co-authored-by: Martin Kröning <mkroening@posteo.net>