added build directory creation process

.github/workflows/ci.yml

@@ -30,6 +30,7 @@ jobs:
         uses: actions/checkout@v2
       - name: Build Arduino examples
         run: |
+          mkdir -p build
           pushd build
           curl -fsSL https://raw.githubusercontent.com/arduino/arduino-cli/master/install.sh | sh
           popd
@@ -41,11 +42,12 @@ jobs:
           sudo apt install -y cmake gcc-arm-none-eabi libnewlib-arm-none-eabi build-essential
       - name: Build rp2040 examples
         run: |
-          cd examples/rp2040
+          pushd examples/rp2040
           git clone --depth=1 https://github.com/raspberrypi/pico-sdk.git
           export PICO_SDK_PATH=$PWD/pico-sdk
           cmake -S . -B build -DPICO_SDK_PATH=$PWD/pico-sdk
           cmake --build build --config Debug
+          popd
   Test:
     runs-on: ubuntu-latest
     needs: Build  # run after Build job