don't build llvm on aarch64.

Author: csyonghe

.github/workflows/ci.yml

@@ -140,6 +140,12 @@ jobs:
                 "-DSLANG_SLANG_LLVM_BINARY_URL=$(pwd)/build/dist-release/slang-llvm.zip" \
                 "-DCMAKE_COMPILE_WARNING_AS_ERROR=${{matrix.warnings-as-errors}}"
               cmake --workflow --preset "${{matrix.config}}"
+            elif [[ "${{ matrix.platform }}" = "aarch64" && "${{ matrix.os }}" = "linux" ]]; then
+              # linux aarch64 cannot build llvm.
+              cmake --preset default --fresh \
+                -DSLANG_SLANG_LLVM_FLAVOR=DISABLE \
+                -DCMAKE_COMPILE_WARNING_AS_ERROR=${{matrix.warnings-as-errors}}
+              cmake --workflow --preset "${{matrix.config}}"
             else
               # Otherwise, use the "system" llvm we have just build or got from the
               # cache in the setup phase
@@ -150,7 +156,7 @@ jobs:
             fi
           fi
       - name: Test Slang
-        if: steps.filter.outputs.should-run == 'true' && matrix.platform != 'wasm'
+        if: steps.filter.outputs.should-run == 'true' && matrix.platform != 'wasm' && matrix.platform != 'aarch64'
         run: |
           export SLANG_RUN_SPIRV_VALIDATION=1
           export SLANG_USE_SPV_SOURCE_LANGUAGE_UNKNOWN=1