try to add clang for rp2040 but pico-sdk does not support that. (got assert.h file not found)

hw/bsp/rp2040/family.cmake

@@ -6,6 +6,12 @@ if (NOT BOARD)
 	set(BOARD pico_sdk)
 endif()
 
+if (TOOLCHAIN STREQUAL "clang")
+	set(PICO_COMPILER "pico_arm_clang")
+else()
+	set(PICO_COMPILER "pico_arm_gcc")
+endif()
+
 # add the SDK in case we are standalone tinyusb example (noop if already present)
 include(${CMAKE_CURRENT_LIST_DIR}/pico_sdk_import.cmake)