Enable Windows Ninja builds
See merge request OpenMW/openmw!202
(cherry picked from commit e0b352323226ff11e230f6489e826df332fa681a)
c1e673ce Unify path conversion functions
fdf0fdbb Fix NMake with MSVC 2019
bdd4a814 Activate MSVC during CMake setup for NMake
eae41050 Support sourcing
c0d28a0e Warn that MSVC environment will need to be activated
bd16ad62 Ninja
7d57e6e2 Support MSVC 2015
3679d329 Check MSVC activated correctly
ed4b73b8 Fix post-2015 Visual Studio
4ffa116a Print message when it's necessary instead of when it isn't
c6e09461 Add instructions for using VS' non-.sln support
d9bb6e63 Activate MSVC later
9ca26358 Create batch script to activate correct MSVC
61df647d Provide scripts to activate selected MSVC in existing shell without kerfuffle