More robust clobbering of ARM builtins on host

[armandomontanez]

Since ARM hosts have builtins listed in hardware/sync.h, these builtins should be clobbered. Newer versions of LLVM/Clang emit an error when clobbering these builtins, so this switches the overrides to use the same patterns as pico_atomic to clobber the builtins.

This works around this compiler error on ARM hosts:

external/pico-sdk+/src/host/hardware_sync/sync_core0_only.c:91:35: error: definition of builtin function '__sev'
   91 | void PICO_WEAK_FUNCTION_IMPL_NAME(__sev)() {
      |                                   ^