Properly output build number

Author: GabrielFleischer

.github/workflows/build.yml

@@ -21,6 +21,8 @@ jobs:
     permissions:
       id-token: write
       contents: write
+    outputs:
+      build-number: ${{ steps.build-gradle.outputs.BUILD_NUMBER }}
     steps:
       - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
       - uses: jdx/mise-action@d6e32c1796099e0f1f3ac741c220a8b7eae9e5dd # v3.2.0