MCPL/NCrystal installation paths on Windows (more of a 'reminder' than an actual issue)

[willend]

Historically the McStas (and partially McXtrace)-provided installation path for MCPL and NCrystal was done with several "not-proper-CMake" hacks that allowed the libs and binaries to exist in the (also not global-standard) install location in e.g. c:\mcstas-3.4\. Many good reasons to do something about that, which we did.

The current state of the main branch uses something "more standard", but leads to MCPL and NCrystal by default being installed within the c:\Program Files folder, which is (currently) not automatically put on the Windows PATH - meaning that the McStas environment does not (without changes) pick them up correctly...

The aim is however that "everything^TM" will eventually become conda-delivered on Windows, which should in fact solve all of these integration-hurdles.

This issue is just put in place to indicate that today's (2024/02) "oldschool" builds via ./buildscripts/build_windows_mcstas do not provide 'out-of-the-box' integration.

FYI @tkittel @mads-bertelsen @farhi