On Windows the limit for command line arguments is 8192 characters, and
this was limiting longer paths with some of our more nested projects
such as Library. Placing the -D arguments into CMAKE_CACHE_ARGS will
write out an initial cache file, that will be passed to CMake with a -C
argument as the initial cache.

By forcing the cache variables we preserve the existing behavior with
-D, to change the values of cache variables in our inner projects.