Probably best illustrated by the fact it's still called OSX, rather than
macOS.

Previously there was an early return, trying to match the same thing.
Making this explicit allows me to more easily add a linux version.

Used for the ppa builds, so it's nice if they still work.

Since I cannot easily change the variable used there, update the autotools codepath to insert the CMake variable.

Not libliblove.so, but liblove-12.0.so, like with autotools.
Note that no liblove.so symlink is created.

And automatically get the timestamp for the changelog too.
That does require an update to cmake 3.7, but as far as I can tell we never use a cmake version older than 3.16 (ubuntu 20.04).

…totools