dev not building with default settings on MSYS2

[Lestropie]

Will be downstream of #2920.

Attempting a build of the latest dev on MSYS2, I get:

[5/503] Running utility command for LinkPythonCommandFiles
FAILED: python/mrtrix3/commands/CMakeFiles/LinkPythonCommandFiles.util
python\mrtrix3\commands\CMakeFiles\LinkPythonCommandFiles.dir\utility.bat d8c87fc7c9db9120
CMake Error: failed to create symbolic link 'C:/msys64/home/rob/src/mrtrix3/build_release/lib/mrtrix3/commands/5ttgen/5ttgen.py': A required privilege is not held by the client.

This can be resolved using -DMRTRIX_PYTHON_SOFTLINK=OFF. However need to determine whether there is some other workaround. Probably not, given that softlink creation usually requires opening a native command prompt. If that's the case, this envvar needs to be forced to ON on MSYS2, with corresponding user warning.

[daljit46]

Assuming you're on Windows 11, you can enable Developer Mode in Settings, which should fix things hopefully.

[Lestropie]

Developer Mode does indeed resolve.

Ideally, if MRTRIX_PYTHON_SOFTLINK=ON, there should be an attempt made at configure time to construct a softlink, and if it fails a suitable error message should be issued.