Fix export file baseline test

Only set up Swift on macOS, since we only support Swift analysis on macOS.

Author: henrymercer

.github/workflows/__export-file-baseline-information.yml

@@ -10,6 +10,7 @@ steps:
       languages: javascript
       tools: ${{ steps.prepare-test.outputs.tools-url }}
   - uses: ./../action/.github/actions/setup-swift
+    if: runner.os == 'macOS'
     with:
       codeql-path: ${{ steps.init.outputs.codeql-path }}
   - name: Build code