feat: add os independent environment variable at parameter xUnitFilePath

[philippleidig]

see #232

[sagatowski]

Looks great! Only one comment. Can you add an example of where it would point to on a Tc/BSD system? So in your example:

- %TC_BOOTPRJPATH% -> e.g. C:\TwinCAT\3.1\Boot\
- %TC_INSTALLPATH% -> e.g. C:\TwinCAT\3.1\

Could you change it to something like:

- %TC_BOOTPRJPATH% -> e.g. C:\TwinCAT\3.1\Boot\ (for Windows), /blabla/ (For Tc/BSD)
- %TC_INSTALLPATH% -> e.g. C:\TwinCAT\3.1\  (for Windows), /blabla/ (For Tc/BSD)

Have obviously no idea what the path on Tc/BSD is.

[philippleidig]

thanks for the hint 👍

[sagatowski]

This is great. Thanks @philippleidig.