Use ruby_thread_set_pthread_native at boot

At boot, `th->ractor->threads.running_ec == th->ec` is true, so calling
ruby_thread_set_native will cause an assertion error.

```
Assertion Failed: ractor_core.h:328:rb_ractor_set_current_ec_:ec == ((void*)0) || cr->threads.running_ec != ec

-- C level backtrace information -------------------------------------------
miniruby(rb_vm_bugreport+0xb60) [0x100290f20] vm_dump.c:1151
miniruby(rb_vm_bugreport) (null):0
miniruby(rb_assert_failure_detail+0xa4) [0x1003b533c] error.c:1168
miniruby(rb_assert_failure_detail+0x0) [0x1003b5298] error.c:1148
miniruby(rb_assert_failure) (null):0
miniruby(Init_native_thread.cold.1+0x0) [0x1003d3c24] ractor_core.h:328
miniruby(rb_ractor_set_current_ec_) (null):0
miniruby(ruby_thread_set_native.cold.1) thread_pthread.c:1624
miniruby(Init_native_thread+0x0) [0x100222380] ractor_core.h:328
miniruby(ruby_thread_set_native) (null):0
miniruby(fiber_entry+0x1c) [0x10008a1c4] cont.c:845
miniruby(coroutine_trampoline+0xa8) [0x1003a1d78] coroutine/pthread/Context.c:148
/usr/lib/system/libsystem_pthread.dylib(_pthread_start+0x88) [0x1911fef94]
```

cont.c

@@ -842,7 +842,7 @@ fiber_entry(struct coroutine_context * from, struct coroutine_context * to)
  rb_thread_t *thread = fiber->cont.saved_ec.thread_ptr;
 
 #ifdef COROUTINE_PTHREAD_CONTEXT
- ruby_thread_set_native(thread);
+ ruby_thread_set_pthread_native(thread);
 #endif
 
  fiber_restore_thread(thread, fiber);

thread_pthread.c

@@ -1607,20 +1607,17 @@ ruby_thread_from_native(void)
 #endif
 }
 
-int
-ruby_thread_set_native(rb_thread_t *th)
+bool
+ruby_thread_set_pthread_native(rb_thread_t *th)
 {
+ RUBY_ASSERT(th->ractor->threads.running_ec == th->ec);
+
  if (th) {
 #ifdef USE_UBF_LIST
  ccan_list_node_init(&th->sched.node.ubf);
 #endif
  }
 
- // setup TLS
-
- if (th && th->ec) {
- rb_ractor_set_current_ec(th->ractor, th->ec);
- }
 #ifdef RB_THREAD_LOCAL_SPECIFIER
  ruby_native_thread = th;
  return 1;
@@ -1629,6 +1626,16 @@ ruby_thread_set_native(rb_thread_t *th)
 #endif
 }
 
+int
+ruby_thread_set_native(rb_thread_t *th)
+{
+ if (th && th->ec) {
+ rb_ractor_set_current_ec(th->ractor, th->ec);
+ }
+
+ return ruby_thread_set_pthread_native(th);
+}
+
 static void native_thread_setup(struct rb_native_thread *nt);
 static void native_thread_setup_on_thread(struct rb_native_thread *nt);
 

thread_pthread.h

@@ -163,4 +163,6 @@ native_tls_set(native_tls_key_t key, void *ptr)
 RUBY_EXTERN native_tls_key_t ruby_current_ec_key;
 #endif
 
+bool ruby_thread_set_pthread_native(struct rb_thread_struct *th);
+
 #endif /* RUBY_THREAD_PTHREAD_H */