Allow free selection and chaining of pipelines

[compor]

Currently, the chaining of pipelines is dependent on knowledge of the internal targets that each pipeline is defining.
This does not allow the free chaining these pipelines.

A solution would be:

• make the pipeline chaining configuration a little more a elaborate, e.g. a cmake fragment/snippet and do not rely on configure-time generation.
• select each pipeline during configuration using their file names, in order to be included.