When cloning repository without specifying the destination,
building documentation works fine. But it fail when the top
level directory is not 'foundatinodb'.
To reproduce:
```
git clone https://github.com/apple/foundationdb.git /tmp/apple-fdb
cd /tmp/apple-fdb/documentation/sphinx
make
```
will result in
```
Exception occurred:
File
"/Users/ssudakovich/.pyenv/versions/2.7.13/lib/python2.7/xml/etree/ElementTree.py", line 647, in parse
source = open(source, "rb")
IOError: [Errno 2] No such file or directory: u'/private/tmp/apple_fdb/documentation/sphinx/../../../foundationdb/versions.target'
```
