Fix for missing xz dependency in gettext.

Fix for:
```
/usr/local/bin/autopoint: line 454: xz: command not found
tar: gettext-0.18.1: Not found in archive
tar: Error exit delayed from previous errors.
autopoint: *** infrastructure files for version 0.18.1 not found; this is autopoint from GNU gettext-tools 0.19.3
autopoint: *** Stop.
```