Add unknown constant to check build time tags

cmd/version.go

@@ -21,13 +21,15 @@ import (
 	"runtime/debug"
 )
 
+const unknown = "unknown"
+
 // var needs to be used instead of const as ldflags is used to fill this
 // information in the release process
 var (
-	kubeBuilderVersion      = "unknown"
-	kubernetesVendorVersion = "unknown"
-	goos                    = "unknown"
-	goarch                  = "unknown"
+	kubeBuilderVersion      = unknown
+	kubernetesVendorVersion = unknown
+	goos                    = unknown
+	goarch                  = unknown
 	gitCommit               = "$Format:%H$" // sha1 from git, output of $(git rev-parse HEAD)
 
 	buildDate = "1970-01-01T00:00:00Z" // build date in ISO8601 format, output of $(date -u +'%Y-%m-%dT%H:%M:%SZ')