make clean removes `pkg/promtail/server/ui/assets_vfsdata.go` which meant the `pkg/promtail/server/ui/assets_vfsdata.go: assets` target is never activated causing a build error, updating to make the target hit on `server.go` which has a dependency on the deleted `assets_vfsdata.go` triggering a run of `make assets` before go builds that file (#555)