Remove unused rb_thread_create_mjit_thread

follow up https://github.com/ruby/ruby/pull/6006

mjit.c

@@ -29,8 +29,6 @@
 
 #include "mjit_worker.c"
 
-extern int rb_thread_create_mjit_thread(void (*worker_func)(void));
-
 // Return an unique file name in /tmp with PREFIX and SUFFIX and
 // number ID.  Use getpid if ID == 0.  The return file name exists
 // until the next function call.

thread_pthread.c

@@ -2156,40 +2156,6 @@ rb_nativethread_self(void)
     return pthread_self();
 }
 
-#if USE_MJIT
-/* A function that wraps actual worker function, for pthread abstraction. */
-static void *
-mjit_worker(void *arg)
-{
-    void (*worker_func)(void) = (void(*)(void))arg;
-
-#ifdef SET_CURRENT_THREAD_NAME
-    SET_CURRENT_THREAD_NAME("ruby-mjitworker"); /* 16 byte including NUL */
-#endif
-    worker_func();
-    return NULL;
-}
-
-/* Launch MJIT thread. Returns FALSE if it fails to create thread. */
-int
-rb_thread_create_mjit_thread(void (*worker_func)(void))
-{
-    pthread_attr_t attr;
-    pthread_t worker_pid;
-    int ret = FALSE;
-
-    if (pthread_attr_init(&attr) != 0) return ret;
-
-    /* jit_worker thread is not to be joined */
-    if (pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED) == 0
-        && pthread_create(&worker_pid, &attr, mjit_worker, (void *)worker_func) == 0) {
-        ret = TRUE;
-    }
-    pthread_attr_destroy(&attr);
-    return ret;
-}
-#endif
-
 int
 rb_sigwait_fd_get(const rb_thread_t *th)
 {

thread_win32.c

@@ -879,29 +879,4 @@ native_thread_native_thread_id(rb_thread_t *th)
 }
 #define USE_NATIVE_THREAD_NATIVE_THREAD_ID 1
 
-#if USE_MJIT
-static unsigned long __stdcall
-mjit_worker(void *arg)
-{
-    void (*worker_func)(void) = arg;
-    rb_w32_set_thread_description(GetCurrentThread(), L"ruby-mjitworker");
-    worker_func();
-    return 0;
-}
-
-/* Launch MJIT thread. Returns FALSE if it fails to create thread. */
-int
-rb_thread_create_mjit_thread(void (*worker_func)(void))
-{
-    size_t stack_size = 4 * 1024; /* 4KB is the minimum commit size */
-    HANDLE thread_id = w32_create_thread(stack_size, mjit_worker, worker_func);
-    if (thread_id == 0) {
-        return FALSE;
-    }
-
-    w32_resume_thread(thread_id);
-    return TRUE;
-}
-#endif
-
 #endif /* THREAD_SYSTEM_DEPENDENT_IMPLEMENTATION */