[CMake] Binary directory on different drive

[Robert Dailey]

I am invoking CMake like this on Windows:

Working directory is: C:\work\build
Directory containing source & root level CMakeLists.txt file: Y:\

So I invoke like this:

C:\work\build> cmake -G "NMake Makefiles" Y:\

When I do this, any subdirectories I traverse inside Y:\ do not appear
under their proper binary directory. Example, let's say I do
add_subdirectory to step into "library", which is at path Y:\library.
The binary directory will be:

C:\work\buildlibrary

Instead of:
C:\work\build\library

The slash between "build" and "library" is missing. Any reason for
this? It doesn't do it if the source & binary directories are on the
same drive letter.