message: Add shared library build
  This changelist adds a Linux shared-library build to GitHub Actions CI.
diff: @@ -20,7 +20,7 @@ jobs:
  compiler: gcc
  compiler_version: "5"
  python: 2.7
  - cmake_config: -DMATERIALX_PYTHON_VERSION=2
  + cmake_config: -DMATERIALX_PYTHON_VERSION=2 -DMATERIALX_BUILD_SHARED_LIBS=ON
  - name: Linux_GCC_6_Python37
  os: ubuntu-latest
  @@ -123,6 +123,10 @@ jobs:
  run: cmake --build . --target install --config ${{env.config}}
  working-directory: build
  + - name: Update Library Path
  + if: runner.os == 'Linux' || runner.os == 'macOS'
  + run: echo "LD_LIBRARY_PATH=$LD_LIBRARY_PATH:$PWD/build/installed/lib" >> $GITHUB_ENV
  +
  - name: Upload Installed Package
  uses: actions/upload-artifact@v2
  with:
  @@ -154,6 +158,6 @@ jobs:
  - name: Python Tests
  run: |
  - cmake -E chdir ../python/MaterialXTest python main.py
  - cmake -E chdir ../python/MaterialXTest python genshader.py
  - working-directory: build
  + python main.py
  + python genshader.py
  + working-directory: python/MaterialXTest
  