Fix windows builds (#538)

Apply the same fix as in raspberrypi/pico-sdk#1846

Author: will-v-pi

.github/workflows/windows.yml

@@ -39,8 +39,7 @@ jobs:
 
       - name: Build Project
         working-directory: ${{github.workspace}}/pico-examples
-        # bash required otherwise this mysteriously (no error) fails at "Generating cyw43_bus_pio_spi.pio.h"
-        shell: bash
+        shell: pwsh
         run: |
           mkdir build
           cd build