Disable dxc source generation

Author: llvm-beanz

.github/workflows/test-all.yaml

@@ -109,7 +109,7 @@ jobs:
             cd DXC
             mkdir build
             cd build
-            cmake -G Ninja -DCMAKE_POLICY_DEFAULT_CMP0141=NEW -DCMAKE_BUILD_TYPE=${{ inputs.BuildType }} -C ${{ github.workspace }}/DXC/cmake/caches/PredefinedParams.cmake -C ${{ github.workspace }}/HLSLTest/cmake/caches/sccache.cmake ${{ github.workspace }}/DXC/
+            cmake -G Ninja -DCMAKE_POLICY_DEFAULT_CMP0141=NEW -DCMAKE_BUILD_TYPE=${{ inputs.BuildType }} -C ${{ github.workspace }}/DXC/cmake/caches/PredefinedParams.cmake -C ${{ github.workspace }}/HLSLTest/cmake/caches/sccache.cmake -DHLSL_DISABLE_SOURCE_GENERATION=On ${{ github.workspace }}/DXC/
             ninja
       - name: Build LLVM
         run: |