Include rsync in Build-Depends-Arch for any build including tools

We normally put "Build-Depends-Arch: rsync" in debian/control based on the control templates for linux-misc-tools or usbip, but those binary packages should be disabled when adding a second linux source package to a suite (e.g. linux-6.12 in bookworm-security).

However we still need rsync when building any tools packages, because it is used in the upstream headers_install target which is a dependency for them. Since this build-dep is not associated with a specific binary package, add it to Build-Depends-Arch in source.control.in with an appropriate build profile qualification.