Calibration files not correctly redirected

[jws-1]

The calibration files written, when using NeXuS files, during gudrun_dcs and purge_det are not redirected as expected. This leads to attempted writes in the StartupFiles directory - this is in issue where Gudrun is packaged alongside other projects, e.g. GudPy, within singularity containers which are read-only - thus, leading to gudrun failing.

This may be an issue with the build pipelines, CMake, or something else. For reference, see #4.