I need to set the Debian control file tag “Multi-Arch: foreign”. I don’t see CPACK_DEBIAN variable to do this.
I think you are right there is no such variable. I don’t think it’s currently possible to add Multi-Arch: tag.
I don’t know any way to add arbitrary tag to Deb package with CPack. This could be useful when no CPACK_DEBIAN_XXXX exists for XXXX.
Something like CPACK_RPM_SPEC_MORE_DEFINE. Another obvious way would be to add the handling of CPACK_DEBIAN_MULTIARCH.
I’ve filed an issue for this.