fix variable assignment

Author: TimHess

.github/workflows/build-and-stage.yml

@@ -35,7 +35,7 @@ jobs:
 
     - name: Detect template source from PR body
       run: |
-        CheckoutTarget = grep "template_checkout_target=" github.event.pull_request.body | awk '{print $2}'
+        CheckoutTarget=$(grep "template_checkout_target=" github.event.pull_request.body | awk '{print $2}')
         if [[ $CheckoutTarget ]]; then
             echo "Found checkout target '$CheckoutTarget' in PR body, using include templates from source."
             echo "{TEMPLATE_CHECKOUT_TARGET}=$CheckoutTarget" >> "$GITHUB_ENV"