Add metadata to feature list for build checks

[9names]

Since I managed to break it in a change, best that CI catches it next time.

[9names]

Looks like I was wrong about metapacs not having their metadata overwritten.
2nd try to fix generate.rs (this time with tests to confirm that it actually works).
Would you like me to remove the regeneration commits?

[diondokter]

That's good to have. The metadata thing is a bit unfortunate, but oh well