Include CPack only when explictly packaging (#5817)
Include CPack only when explictly packaging (#5817)

Including CPack without the additional packaging information creates unused project files, and can potentially cause issues for projects including Flatbuffers that also use CPack.
google/flatbuffers,google/flatbuffers,DavadDi/flatbuffers,evolutional/flatbuffers,google/flatbuffers,alexames/flatbuffers,pjulien/flatbuffers,alexames/flatbuffers,alexames/flatbuffers,pjulien/flatbuffers,google/flatbuffers,google/flatbuffers,google/flatbuffers,pjulien/flatbuffers,alexames/flatbuffers,pjulien/flatbuffers,alexames/flatbuffers,google/flatbuffers,google/flatbuffers,evolutional/flatbuffers,google/flatbuffers,google/flatbuffers,evolutional/flatbuffers,evolutional/flatbuffers,DavadDi/flatbuffers,evolutional/flatbuffers,alexames/flatbuffers,alexames/flatbuffers,alexames/flatbuffers,pjulien/flatbuffers,alexames/flatbuffers,DavadDi/flatbuffers,alexames/flatbuffers,google/flatbuffers,evolutional/flatbuffers,alexames/flatbuffers,alexames/flatbuffers,evolutional/flatbuffers,pjulien/flatbuffers,pjulien/flatbuffers,alexames/flatbuffers,evolutional/flatbuffers,alexames/flatbuffers,DavadDi/flatbuffers,google/flatbuffers,pjulien/flatbuffers,DavadDi/flatbuffers,pjulien/flatbuffers,evolutional/flatbuffers,alexames/flatbuffers,evolutional/flatbuffers,evolutional/flatbuffers,evolutional/flatbuffers,google/flatbuffers,pjulien/flatbuffers,DavadDi/flatbuffers,google/flatbuffers,pjulien/flatbuffers,pjulien/flatbuffers,google/flatbuffers,evolutional/flatbuffers