cmake: Ensure source and binary dirs are set
If only the source dir is provided, the binary dir is assumed
to be the working directory. If only the binary dir is provided
and it doesn't yet have a CMakeCache.txt to provide the
source dir, then the source dir is assumed to be the working
directory. This logic was not previously being handled
correctly when -S and/or -B options were involved.
Furthermore, when both were missing, no suitable error
message was provided and an empty string was used for
the build directory.
Fixes: #18707
5 files changed
