[FOLD] use ninja when building llvm

Author: sdkrystian

.github/workflows/ci.yml

@@ -326,6 +326,7 @@ jobs:
           build-type: ${{ matrix.build-type }}
           cc: ${{ steps.setup-cpp.outputs.cc }}
           cxx: ${{ steps.setup-cpp.outputs.cxx }}
+          generator: Ninja
           install: true
           install-prefix: ${sourceDir}/../install
           run-tests: false