Merge all artifacts into a single zip file

Since `upload-artifact@v4` we're no longer allowed to upload to a single
artifact from multiple jobs.  Fortunately GitHub provides a helper step
to merge them again, giving us a single artifact to download rather than
having to download+open+unzip four individual ones.

Author: MarijnS95

.github/workflows/build-dxc.yaml

@@ -4,12 +4,12 @@ jobs:
   build-dxc-macos:
     runs-on: macos-15-xlarge
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - run: git clone https://github.com/microsoft/DirectXShaderCompiler.git dxc --revision=$(cat commit-hash) --recurse-submodules
       - run: cmake -Bbuild -GNinja -C cmake/caches/PredefinedParams.cmake -DSPIRV_BUILD_TESTS=OFF -DCMAKE_BUILD_TYPE=Release -DLLVM_ENABLE_WERROR=OFF
         working-directory: dxc
       - run: cmake --build dxc/build -t dxcompiler
-      - uses: actions/upload-artifact@v4
+      - uses: actions/upload-artifact@v6
         with:
           name: MacOS aarch64 libdxcompiler.dylib
           path: dxc/build/lib/libdxcompiler.dylib
@@ -18,12 +18,12 @@ jobs:
     runs-on: ubuntu-22.04 # For older GLIBC, the "hosted runner" above has Ubuntu 24.04 whose compiled binaries require glibc 2.38.
     steps:
       - run: sudo apt-get install -y ninja-build
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - run: git clone https://github.com/microsoft/DirectXShaderCompiler.git dxc --revision=$(cat commit-hash) --recurse-submodules
       - run: cmake -Bbuild -GNinja -C cmake/caches/PredefinedParams.cmake -DSPIRV_BUILD_TESTS=OFF -DCMAKE_BUILD_TYPE=Release -DLLVM_ENABLE_WERROR=OFF
         working-directory: dxc
       - run: cmake --build dxc/build -t dxcompiler
-      - uses: actions/upload-artifact@v4
+      - uses: actions/upload-artifact@v6
         with:
           name: Linux x64 libdxcompiler.so
           path: dxc/build/lib/libdxcompiler.so
@@ -34,12 +34,12 @@ jobs:
     # 19045.6691 is the latest/last Windows 10 release, which we need to target in order
     # to load dxcompiler.dll on our older GPU-runner CI machines.
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - run: git clone https://github.com/microsoft/DirectXShaderCompiler.git dxc --revision=$(cat commit-hash) --recurse-submodules
       - run: cmake -Bbuild -G "Visual Studio 17 2022" -C cmake/caches/PredefinedParams.cmake -DSPIRV_BUILD_TESTS=OFF -DLLVM_ENABLE_WERROR=OFF -DCMAKE_SYSTEM_VERSION="10.0.19045.6691"
         working-directory: dxc
       - run: cmake --build dxc/build --config Release -t dxcompiler
-      - uses: actions/upload-artifact@v4
+      - uses: actions/upload-artifact@v6
         with:
           name: Windows x64 dxcompiler.dll
           path: dxc/build/Release/bin/dxcompiler.*
@@ -55,7 +55,20 @@ jobs:
           -DCLANG_TABLEGEN="$(Resolve-Path build\Release\bin\clang-tblgen.exe)"
         working-directory: dxc
       - run: cmake --build dxc/build-aarch64 --config Release -t dxcompiler
-      - uses: actions/upload-artifact@v4
+      - uses: actions/upload-artifact@v6
         with:
           name: Windows aarch64 dxcompiler.dll
           path: dxc/build-aarch64/Release/bin/dxcompiler.*
+
+  merge:
+    runs-on: ubuntu-latest
+    needs:
+      - build-dxc-macos
+      - build-dxc-linux
+      - build-dxc-windows
+    steps:
+      - name: Merge Artifacts
+        uses: actions/upload-artifact/merge@v6
+        with:
+          name: dxcompiler
+          pattern: "*dxcompiler*"