ci: use correct ccache compiler for aarch64 cross compile

.github/workflows/build.yml

@@ -38,7 +38,7 @@ jobs:
       - name: Set git safe directory
         run: git config --global safe.directory '*'
       - name: Make
-        run: make -C ${{ matrix.variant }} CC="ccache gcc" compile
+        run: make -C ${{ matrix.variant }} CC="ccache aarch64-linux-gnu-gcc" compile
       - name: Upload artifacts
         uses: actions/upload-artifact@v4
         with: