git-artifacts: avoid linter warning

The linter has a hard time recognizing `core.setOutput()`. However,
every `github-script` step has a naturally-defined output: `result`, set
to the return value of the script. Let's use that instead.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Author: dscho

.github/workflows/git-artifacts.yml

@@ -45,7 +45,7 @@ jobs:
   pkg:
     runs-on: ${{ github.event.inputs.architecture == 'aarch64' && fromJSON('["Windows", "ARM64"]') || 'windows-latest' }}
     outputs:
-      artifact_matrix: ${{steps.artifact-build-matrix.outputs.matrix}}
+      artifact_matrix: ${{ steps.artifact-build-matrix.outputs.result }}
       msystem: ${{steps.configure-environment.outputs.MSYSTEM}}
       mingw_package_prefix: ${{steps.configure-environment.outputs.MINGW_PACKAGE_PREFIX}}
       sdk_repo_arch: ${{steps.configure-environment.outputs.SDK_REPO_ARCH}}
@@ -195,7 +195,7 @@ jobs:
             try {
               const output = createArtifactsMatrix(process.env.ARTIFACTS_TO_BUILD, process.env.ARCHITECTURE)
               core.info(`Will be using the following matrix: ${JSON.stringify(output)}`)
-              core.setOutput('matrix', output)
+              return output
             } catch (e) {
               core.setFailed(e.message)
             }