pkg/build: use noinst_DATA instead of _SCRIPTS
pkg/build: use noinst_DATA instead of _SCRIPTS

The manifest.json files are data, not scripts, so use the appropriate
variable for them.

martinpitt/cockpit,cockpit-project/cockpit,martinpitt/cockpit,mvollmer/cockpit,mvollmer/cockpit,cockpit-project/cockpit,martinpitt/cockpit,cockpit-project/cockpit,martinpitt/cockpit,cockpit-project/cockpit,cockpit-project/cockpit,martinpitt/cockpit,mvollmer/cockpit,mvollmer/cockpit,mvollmer/cockpit