global handler.
## How to use?
```ignore
let ptr = HANDLER.load(Ordering::Acquire);
if !ptr.is_null(){
let logger: IartLogger = unsafe { core::mem::transmute(ptr) };
}
```
or
```ignore
let ptr = HANDLER.load(Ordering::Acquire);
if !ptr.is_null() {
let logger: IartLogger<A> = unsafe { core::mem::transmute(ptr) };
}
```