On non-Windows platforms libuv assumes that file descriptors 0-2 are
always used for standard pipes and never for anything else.  Otherwise,
libuv may re-use one of these descriptors and then fail an assertion
when closing it.  Similarly, On Windows platforms our ConsoleBuf
implementation assumes that the standard handles are always open.

If CMake is run with any standard pipes closed, open them with
`/dev/null` or `NUL` to satisfy these assumptions.

Fixes: #19219