COMP: Workaround actions/checkout limitation

This addresses the following error:

  Error: Repository path '/home/runner/work/SlicerDMRI/Slicer' is not under '/home/runner/work/SlicerDMRI/SlicerDMRI'

See actions/checkout#197

.github/workflows/build-test.yml

@@ -32,7 +32,13 @@ jobs:
       uses: actions/checkout@v3
       with:
         repository: Slicer/Slicer
-        path: ${{ github.workspace }}/../Slicer
+        path: ${{ github.workspace }}/Slicer
+
+      # Workaround issue https://github.com/actions/checkout/issues/197 preventing
+      # the checkout outside of the GitHub workspace.
+    - name: Finalize Slicer checkout
+      run: |
+        mv ${{ github.workspace }}/Slicer ${{ github.workspace }}/../Slicer
 
     - id: slicer-build
       name: Build Slicer