@daithi-coombes We can't have hardcoded or ~ paths in the build script; everything needs to be relative to the Rakefile.

Reason is that on the build server, the build happens in a different folder, depending on how the agent is configured.

eg: http://ci.labs.cityindex.com:8080/view/pressupbox-development-boilerplate/job/pressupbox-development-boilerplate/6/console
```
Running "compile-buildpack" task
-----> compile params: BUILDPACK_DIR: /var/lib/jenkins/workspace/pressupbox-development-boilerplate/buildpack BUILD_DIR: ./dist CACHE_DIR:./.buildpack-cache
-----> Installing HipHop v2.0.0
       Extracting ./.buildpack-cache/hiphop-php-2.0.0.tar.gz to /var/lib/jenkins/workspace/pressupbox-development-boilerplate/dist/runtimes/hiphop-php
```