Add difftests to CI.

Author: LegNeato

.github/workflows/ci.yaml

@@ -42,6 +42,13 @@ jobs:
       - if: ${{ runner.os == 'Linux' }}
         name: Linux - Install native dependencies
         run: sudo apt install libwayland-cursor0 libxkbcommon-dev libwayland-dev
+      - if: ${{ runner.os == 'Linux' }}
+        name: Install xvfb, llvmpipe and lavapipe
+        run: |
+          sudo apt-get update -y -qq
+          sudo add-apt-repository ppa:kisak/turtle -y
+          sudo apt-get update
+          sudo apt install -y xvfb libgl1-mesa-dri libxcb-xfixes0-dev mesa-vulkan-drivers
       # cargo version is a random command that forces the installation of rust-toolchain
       - name: install rust-toolchain
         run: cargo version
@@ -64,6 +71,10 @@ jobs:
         if: ${{ matrix.target != 'aarch64-linux-android' }}
         run: cargo run -p compiletests --release --no-default-features --features "use-installed-tools" -- --target-env vulkan1.1,vulkan1.2,spv1.3
 
+      - name: difftest
+        if: ${{ matrix.target != 'aarch64-linux-android' }}
+        run: cargo run -p difftests --release --no-default-features --features "use-installed-tools"
+
       - name: workspace test
         if: ${{ matrix.target != 'aarch64-linux-android' }}
         run: cargo test --release