Can't get correct instance type when extending from Error and target es5.

[wangzishi]

TypeScript Version: 2.4.2

Code

class MyError extends Error {
    constructor(msg: any) {
        super(msg);
    }
}

let err = new MyError('msg');

console.log(err instanceof MyError);

Expected behavior:
true

Actual behavior:
err instanceof MyError return false, and err is an instance of Error.

[j-oliveras]

This is a breaking change since Typescript 2.1.

[DanielRosenwasser]

Duplicate of #12123.