Fix: Make build and dev dependencies optional

[sarahec]

This fixes #170

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[PeterStaar-IBM]

@sarahec What does this solve?

[sarahec]

@sarahec What does this solve?

Look at #170. The build and dev dependency groups are getting merged into the final product; this marks them correctly as optional as they're only meant to be used during development. (Notice that in the workflow scripts you're explicitly excluding cmake and the other build-only tools which shouldn't have been there in the first place.)