Add ccache to WASM playground workflow

Author: cs01

.github/workflows/build-playground.yml

@@ -24,7 +24,15 @@ jobs:
       - name: Install dependencies
         run: |
           sudo apt-get update
-          sudo apt-get install -y ninja-build cmake
+          sudo apt-get install -y ninja-build cmake ccache
+
+      - name: Setup ccache
+        uses: actions/cache@v4
+        with:
+          path: ~/.ccache
+          key: ccache-wasm-${{ github.sha }}
+          restore-keys: |
+            ccache-wasm-
 
       - name: Configure WASM build (Null-Safe Clang)
         run: |
@@ -44,6 +52,8 @@ jobs:
             -DLLVM_ENABLE_TERMINFO=OFF \
             -DLLVM_ENABLE_ZLIB=OFF \
             -DLLVM_ENABLE_LIBXML2=OFF \
+            -DCMAKE_C_COMPILER_LAUNCHER=ccache \
+            -DCMAKE_CXX_COMPILER_LAUNCHER=ccache \
             -DCMAKE_EXE_LINKER_FLAGS="-sEXPORTED_RUNTIME_METHODS=callMain -sEXIT_RUNTIME=0 -sALLOW_MEMORY_GROWTH=1" \
             ../llvm