Data file path is resolved differently in a build directory within the project

[php1ic]

Assuming the project is checkout out to - /some/path/inch/

A parallel build directory at /some/path/build/ will resolve the data path correctly and use the absolute path.
A build directory within the project at /some/path/inch/build will not resolve correctly and tests will fail (see #21).

Need to investigate why, the macro __FILE__ seems to behave differently depending on build directory location.