Clean (2) installers/ubuntu/build

Clean installers/ubuntu/build;

Please test it well.

This pull fix pull #1109 
No need to use escape characters:
```python
os.system("rm -vf '%s'" % packageName)
```

By the way, can you explain why `os.unlink` is not enough? If you want to remove a whole tree, better use [shutil.rmtree](https://docs.python.org/2/library/shutil.html#shutil.rmtree) than a bare shell command.