message: Update software rendering in GitHub Actions
  This changelist updates software rendering to llvmpipe in the GitHub Actions CI for MaterialX.
  This reduces the time spent in software rendering by roughly a factor of ten, and allows us to increase our rendering resolution from 48x48 to 128x128 without a noticeable performance penalty.
diff: @@ -111,7 +111,7 @@ jobs:
  if: runner.os == 'Linux'
  run: |
  sudo apt-get update
  - sudo apt-get install libglu1-mesa-dev xorg-dev
  + sudo apt-get install xorg-dev mesa-utils
  if [ "${{ matrix.compiler }}" = "gcc" ]; then
  sudo apt-get install -y g++-${{ matrix.compiler_version }} g++-${{ matrix.compiler_version }}-multilib
  echo "CC=gcc-${{ matrix.compiler_version }}" >> $GITHUB_ENV
  @@ -223,9 +223,8 @@ jobs:
  run: |
  Xvfb :1 -screen 0 1280x960x24 &
  echo "DISPLAY=:1" >> $GITHUB_ENV
  - echo "MESA_GL_VERSION_OVERRIDE=4.0FC" >> $GITHUB_ENV
  - echo "MESA_GLSL_VERSION_OVERRIDE=400" >> $GITHUB_ENV
  - echo "GALLIUM_DRIVER=softpipe" >> $GITHUB_ENV
  + echo "LIBGL_ALWAYS_SOFTWARE=1" >> $GITHUB_ENV
  + echo "GALLIUM_DRIVER=llvmpipe" >> $GITHUB_ENV
  - name: Render Script Tests
  if: matrix.test_render == 'ON'
  @@ -237,8 +236,8 @@ jobs:
  - name: Viewer Tests
  if: matrix.test_render == 'ON'
  run: |
  - ../installed/bin/MaterialXView --material brass_average_baked.mtlx --mesh ../../resources/Geometry/sphere.obj --screenWidth 48 --screenHeight 48 --cameraZoom 1.4 --shadowMap false --captureFilename Viewer_BrassAverage.png
  - ../installed/bin/MaterialXView --material usd_preview_surface_carpaint.mtlx --mesh ../../resources/Geometry/sphere.obj --screenWidth 48 --screenHeight 48 --cameraZoom 1.4 --shadowMap false --captureFilename Viewer_CarpaintTranslated.png
  + ../installed/bin/MaterialXView --material brass_average_baked.mtlx --mesh ../../resources/Geometry/sphere.obj --screenWidth 128 --screenHeight 128 --cameraZoom 1.4 --shadowMap false --captureFilename Viewer_BrassAverage.png
  + ../installed/bin/MaterialXView --material usd_preview_surface_carpaint.mtlx --mesh ../../resources/Geometry/sphere.obj --screenWidth 128 --screenHeight 128 --cameraZoom 1.4 --shadowMap false --captureFilename Viewer_CarpaintTranslated.png
  working-directory: build/render
  - name: Upload Installed Package
  