[PATCH] build: explicitly specify Makefile generator

[Eicke Herbertz]

> 
> Where does that CMAKE_GENERATOR environment variable come from? Would
> it make sense to undefine it instead?
> 
> Regards,
> Jonas

Well, from the environment of my development machine.
I have it set to Ninja for a long time on this system.

Do you mean undefining it manually or as part of the build process?

I'd dislike having to manually undefine it. It's a documented behaviour
of CMake since v3.15 and it's tedious to run "make -j1 V=s" to figure
out the issue first.

As part of the build process, I find explicitly defining the Makefile
generator better communicates intent than undefining an environment 
variable and depending on CMake's default (although that probably won't 
change).

Regards,
Eicke