build GHA: Address set-output deprecation warnings

.github/workflows/build.yml

@@ -33,7 +33,7 @@ jobs:
         # version, because "goenv" can react to it automatically.
         run: |
           echo "Building with Go $(cat .go-version)"
-          echo "::set-output name=go-version::$(cat .go-version)"
+          echo "go-version=$(cat .go-version)" >> $GITHUB_OUTPUT
 
   set-product-version:
     runs-on: ubuntu-latest
@@ -52,7 +52,7 @@ jobs:
         id: set-ld-flags
         run: |
           T="github.com/hashicorp/packer/version"
-          echo "::set-output name=set-ld-flags::-s -w -X ${T}.GitCommit=${GITHUB_SHA::8} -X ${T}.GitDescribe=${{ steps.set-product-version.outputs.product-version }} -X ${T}.Version=${{ steps.set-product-version.outputs.base-product-version }} -X ${T}.VersionPrerelease=${{ steps.set-product-version.outputs.prerelease-product-version }} -X ${T}.VersionMetadata="
+          echo "set-ld-flags='-s -w -X ${T}.GitCommit=${GITHUB_SHA::8} -X ${T}.GitDescribe=${{ steps.set-product-version.outputs.product-version }} -X ${T}.Version=${{ steps.set-product-version.outputs.base-product-version }} -X ${T}.VersionPrerelease=${{ steps.set-product-version.outputs.prerelease-product-version }} -X ${T}.VersionMetadata='" >> $GITHUB_OUTPUT
       - name: validate outputs
         run: |
           echo "Product Version: ${{ steps.set-product-version.outputs.product-version }}"