cmake: Pass -S and -B into PreLoad.cmake and -C scripts

Before this, it was not possible to see what the source or build directories were set to on the command line.

As far as I can tell, the old behaviour was defined as a bugfix in 9be34138, but it is unclear what bug was being fixed, and the fixed behaviour seemingly wasn't being defended by any test.

Fixes: #19619 (closed)
Topic-rename: cmake-initial-cache-dirs