runtime: avoid duplicate task exit symbol

src/internal/task/task_threads.c

@@ -146,7 +146,7 @@ void* tinygo_task_current(void) {
 }
 
 // Exit the current thread.
-void tinygo_task_exit(void) {
+void tinygo_task_exit_thread(void) {
     pthread_exit(NULL);
 }
 

src/internal/task/task_threads.go

@@ -336,7 +336,7 @@ func tinygo_task_init(t *Task, thread *threadID, numCPU *int32)
 //go:linkname tinygo_task_start tinygo_task_start
 func tinygo_task_start(fn uintptr, args unsafe.Pointer, t *Task, thread *threadID, stackTop *uintptr, stackSize uintptr) int32
 
-//go:linkname tinygo_task_exit tinygo_task_exit
+//go:linkname tinygo_task_exit tinygo_task_exit_thread
 func tinygo_task_exit()
 
 // Pause the thread by sending it a signal.