message: Split gltfpack build into a separate target
  This is just for clarity wrt GH display.
diff: @@ -16,6 +16,8 @@ jobs:
  make -j2 config=sanitize test
  make -j2 config=debug test
  make -j2 config=release test
  + - name: make gltfpack
  + run: |
  make -j2 config=release gltfpack
  strip gltfpack
  - name: make coverage
  