split -abc="def" into -abc def

sometime we need to use this:

```
-browsers="chrome"
```

it will be splited into `-b -r -o -w -s -e -r -s -= -" -c -h -r -o -m -e -"`...

It`s **not** what we want

after change. 

```
-browser --> -b -r -o -w -s -e -r
-browser="chrome" --> --browser chorme
```