An issue and the solution for compiling on the arm64 system

Dear expert, When I was creating a docker image of Corryvreckan based on arm64 (I mainly use a macOS with an M series, the default pulled image does not run smoothly), I found that Corryvreckan could not compile and got an error related to the use of abs and casting at this line.

https://gitlab.cern.ch/corryvreckan/corryvreckan/-/blob/master/src/core/detector/PixelModuleDetector.cpp?ref_type=heads#L128

The issue can be resolved by replacing abs() with fabs(), and using static_cast<double>(transformed_big_pixel_x[i]), and then there are no issues with compilation or usage. In fact, I noticed that everywhere else in PixelModuleDetector.cpp, fabs() and static_cast are already used, and there is nothing particularly special about this part.

Could you please consider fixing this?