Update template/.github/workflows/build.yml.j2

Co-authored-by: Nick <10092581+NickLarsenNZ@users.noreply.github.com>

Author: adwk67

template/.github/workflows/build.yml.j2

@@ -423,9 +423,11 @@ jobs:
       - name: Update version if PR against non-main branch
         # For PRs to be merged against a release branch, use the version that has already been set in the calling script.
         if: ${{ github.event_name == 'pull_request' && github.ref != 'refs/heads/main' }}
+        env:
+          PR_NUMBER: ${{ github.event.pull_request.number }}
         run: |
           MANIFEST_VERSION=$(cargo metadata --format-version 1 --no-deps | jq -r '.packages[0].version')
-          PR_VERSION="${MANIFEST_VERSION}-pr${{ github.event.pull_request.number }}"
+          PR_VERSION="${MANIFEST_VERSION}-pr${PR_NUMBER}"
           cargo set-version --offline --workspace "$PR_VERSION"
       - name: Build manifest list
         run: |