fix(build): build-install-yaml needs to tolerate $1 being unset. Oops. (#4319)

Signed-off-by: Flynn <emissary@flynn.kodachi.com>

Author: kflynn

hack/build-install-yaml.sh

@@ -15,7 +15,6 @@
 # limitations under the License.
 
 set -o errexit
-set -o nounset
 set -o pipefail
 
 CHANNELS=(standard experimental)
@@ -25,6 +24,8 @@ if [ "$1" == "--experimental-only" ]; then
     shift
 fi
 
+set -o nounset
+
 readonly YEAR=$(date +"%Y")
 
 mkdir -p release/