Update build.yml

Author: sfe-SparkFro

.github/workflows/build.yml

@@ -13,7 +13,7 @@ jobs:
     - name: Install packages
       run: sudo apt-get install gcc-arm-none-eabi libnewlib-arm-none-eabi
     - name: Set Pico SDK path
-      run: export PICO_SDK_PATH=$GITHUB_WORKSPACE/micropython/lib/pico-sdk
+      run: echo "{PICO_SDK_PATH}={$GITHUB_WORKSPACE/micropython/lib/pico-sdk}" >> "$GITHUB_ENV"
     - name: Build OpenCV
       run: make -C src/opencv PLATFORM=embedded/rp2350
     - name: Build MPY Cross