[CMake] Difficulties with component search by "FindBoost"

[SF Markus Elfring]

> Perhaps, all headers-only libraries could be handled by the FindBoost module

I would appreciate if corresponding CMake scripts will consider a better
handling for such software.


> and then reported by CMake:
> "Spirit is headers-only, shall not be specified with COMPONENTS"

I would prefer a different feedback. Can the specification of "non-binary
components" be also tolerated there?

Regards,
Markus