SFT-4357: Fix -Werror=dangling-pointer.

Due to the update to Ubuntu 24.04 on the CI it causes this warning to be
emitted, and as a result the build fails.

This code takes the pointer of a variable on the stack to measure the
stack usage.

* py/stackctrl.c: Disable -Wdangling-pointer warning.

py/stackctrl.c

@@ -29,6 +29,7 @@
 
 void mp_stack_ctrl_init(void) {
     volatile int stack_dummy;
+#pragma GCC diagnostic warning "-Wdangling-pointer"
     MP_STATE_THREAD(stack_top) = (char *)&stack_dummy;
 }
 
@@ -39,6 +40,7 @@ void mp_stack_set_top(void *top) {
 mp_uint_t mp_stack_usage(void) {
     // Assumes descending stack
     volatile int stack_dummy;
+#pragma GCC diagnostic warning "-Wdangling-pointer"
     return MP_STATE_THREAD(stack_top) - (char *)&stack_dummy;
 }