Split CI to build and test jobs (#8359)

The CI has been re-organized with the following:
```
ci.yml (Main Orchestrator)
├── filter job
│   ├── Documentation Only? → Yes → Skip CI
│   └── Documentation Only? → No → Continue CI
│
├── Build Jobs
│   └── ci-slang-build.yml
│       ├── common-setup action
│       ├── Build & Package
│       └── Upload Artifacts (Build package and Tests package)
│
└── Test Jobs
    └── ci-slang-test.yml
        └── common-test-setup action
            ├── Download Tests Artifacts ← (from Build)
            └── Run Tests
```

To achieve fine-grained build->test dependency, instead of using `matrix
strategy` in single build (or single test) job, the main ci.yml
statically defines the each config of the build and test job.
e.g. `build-windows-debug-cl-x86_64-gpu` and
`test-windows-debug-cl-x86_64-gpu` are a pair of the build-test job for
the windows/debug/ci config.


Closes: https://github.com/shader-slang/slang/issues/6728

---------

Co-authored-by: slangbot <ellieh+slangbot@nvidia.com>
Co-authored-by: slangbot <186143334+slangbot@users.noreply.github.com>

2 files changed, 112 insertions, 6 deletions

diff --git a/.github/actions/common-setup/action.yml b/.github/actions/common-setup/action.yml
index f2e9567dd..1ab2d1a48 100644
--- a/.github/actions/common-setup/action.yml
+++ b/.github/actions/common-setup/action.yml
@@ -28,6 +28,20 @@ runs:
       with:
         sdk: "10.0.19041.0"
 
+    - name: Install dependencies (Linux only)
+      shell: bash
+      run: |
+        if [[ "${{ inputs.os }}" == "linux" ]]; then
+            sudo apt-get update
+            sudo apt-get install -y libx11-dev 
+        fi
+
+    - name: Setup Node.js (Linux only)
+      if: inputs.os == 'linux'
+      uses: actions/setup-node@v4
+      with:
+        node-version: "20.x"
+
     - shell: bash
       run: |
         # Set up system dependencies
@@ -84,7 +98,7 @@ runs:
       id: cache-llvm
       if: inputs.build-llvm == 'true'
       with:
-        path: ${{ github.workspace }}/build/llvm-project-install
+        path: build/llvm-project-install
         # Use os*compiler*platform in lieu of an ABI key here, which is what we really want
         key: llvm-${{ inputs.os }}-${{ inputs.compiler }}-${{ inputs.platform }}-${{ hashFiles('external/build-llvm.sh') }}
     - name: Build LLVM
@@ -97,7 +111,7 @@ runs:
     - uses: actions/cache/save@v4
       if: inputs.build-llvm == 'true' && steps.cache-llvm.outputs.cache-hit != 'true'
       with:
-        path: ${{ github.workspace }}/build/llvm-project-install
+        path: build/llvm-project-install
         key: ${{ steps.cache-llvm.outputs.cache-primary-key }}
 
     - name: Set environment variable for CMake
@@ -133,12 +147,15 @@ runs:
           exit 0
         fi
 
-        echo "✅ ccache found on self-hosted runner - setting up local caching"
+        echo "✅ ccache found on self-hosted runner - setting up persistent caching"
 
-        # Set ccache directory (local temp directory)
-        ccache_dir="${{ github.workspace }}/.ccache-local"
+        # Set ccache directory to a persistent location outside workspace
+        # Use runner temp directory with a unique path per repo/compiler/platform
+        ccache_base_dir="${RUNNER_TEMP:-/tmp}/ccache-slang"
+        ccache_dir="$ccache_base_dir/${{ inputs.os }}-${{ inputs.compiler }}-${{ inputs.platform }}"
         mkdir -p "$ccache_dir"
         echo "CCACHE_DIR=$ccache_dir" >> $GITHUB_ENV
+        echo "🔧 Using persistent ccache directory: $ccache_dir"
 
         # Configure ccache settings for local use only
         ccache --set-config=max_size=2G
@@ -147,7 +164,9 @@ runs:
         ccache --set-config=sloppiness=pch_defines,time_macros
 
         # Enable ccache for CMake (set environment variables)
-        echo "ccache_symlinks_path=ccache" >> $GITHUB_ENV
+        # Get the full path to ccache executable
+        ccache_path=$(which ccache)
+        echo "ccache_symlinks_path=$ccache_path" >> $GITHUB_ENV
 
         # Show initial stats
         echo "ccache configuration:"
diff --git a/.github/actions/common-test-setup/action.yml b/.github/actions/common-test-setup/action.yml
new file mode 100644
index 000000000..ab1a665c7
--- /dev/null
+++ b/.github/actions/common-test-setup/action.yml
@@ -0,0 +1,87 @@
+name: Common Test Setup
+description: "Common setup steps for Slang test jobs"
+
+inputs:
+  os:
+    required: true
+    description: "Operating system"
+  compiler:
+    required: true
+    description: "Compiler to use"
+  platform:
+    required: true
+    description: "Platform to build for"
+  config:
+    required: true
+    description: "Build configuration"
+
+runs:
+  using: "composite"
+  steps:
+    - name: Setup
+      uses: ./.github/actions/common-setup
+      with:
+        os: ${{ inputs.os }}
+        compiler: ${{ inputs.compiler }}
+        platform: ${{ inputs.platform }}
+        config: ${{ inputs.config }}
+        build-llvm: false
+
+    - uses: actions/download-artifact@v4
+      with:
+        name: slang-tests-${{ inputs.os }}-${{ inputs.platform }}-${{ inputs.compiler }}-${{ inputs.config }}
+        path: github_artifact
+
+    - name: Setup environment
+      shell: bash
+      run: |
+        # Artifacts are now directly extracted to github_artifact directory
+        # Just ensure all executables are executable
+        chmod +x github_artifact/${cmake_config}/bin/* 2>/dev/null || echo "No executables to make executable"
+
+        # Set up bin_dir based on platform and config
+        if [[ "${{ inputs.platform }}" == "wasm" ]]; then
+          bin_dir=build.em/Release/bin
+          echo "bin_dir=$bin_dir" >> $GITHUB_ENV
+        else
+          bin_dir=$(pwd)/github_artifact/${cmake_config}/bin
+          echo "bin_dir=$bin_dir" >> $GITHUB_ENV
+        fi
+
+        # Also set lib_dir for slangpy tests
+        lib_dir=$(pwd)/github_artifact/${cmake_config}/lib
+        echo "lib_dir=$lib_dir" >> $GITHUB_ENV
+
+        # Set up library path for runtime linking
+        if [[ "${{ inputs.os }}" == "linux" ]]; then
+          echo "LD_LIBRARY_PATH=${lib_dir}:$LD_LIBRARY_PATH" >> $GITHUB_ENV
+        elif [[ "${{ inputs.os }}" == "macos" ]]; then
+          echo "DYLD_LIBRARY_PATH=${lib_dir}:$DYLD_LIBRARY_PATH" >> $GITHUB_ENV
+        elif [[ "${{ inputs.os }}" == "windows" ]]; then
+          # On Windows, DLLs should be in the same directory as executables or in PATH
+          # Use $GITHUB_PATH instead of $PATH for preservation across steps and
+          # avoid unix-like/windows-like path issues
+          echo "$bin_dir" >> $GITHUB_PATH
+          echo "$lib_dir" >> $GITHUB_PATH
+        fi
+
+    - name: Check runtime environment
+      if: inputs.platform != 'wasm'
+      shell: bash
+      run: |
+        echo "$bin_dir/slang-test"
+        "$bin_dir/slang-test" tests/render/check-backend-support-on-ci.slang
+        smokeResult=$("$bin_dir/slang-test" tests/render/check-backend-support-on-ci.slang)
+        supportedBackends="$(echo "$smokeResult" | grep 'Supported backends: ')"
+        echo "$supportedBackends"
+        # Windows-specific version checks - fail if tools are not available
+        if [[ "${{ inputs.os }}" == "windows" ]]; then
+          echo "Printing CUDA compiler version: ..."
+          nvcc --version || (echo "ERROR: CUDA compiler (nvcc) not available on Windows" && exit 1)
+          echo "Printing GPU driver version: ..."
+          nvidia-smi -q | grep Version || (echo "ERROR: NVIDIA driver (nvidia-smi) not available on Windows" && exit 1)
+          echo "Printing Vulkan SDK version: ..."
+          vulkaninfo | grep -i version || (echo "ERROR: Vulkan SDK (vulkaninfo) not available on Windows" && exit 1)
+        fi        
+        echo "All environment variables:"
+        env | sort