Change the current working directory to the open file descriptor
'fildes'.
On Unix systems the fchdir() function is similar to the chdir()
function except it uses an open file descriptor to change the
current working directory for the process instead of a
pathname.
On Windows there is not a matching function or one with similar
functionality. The source code will need to be changed for Windows
to track the pathname or preserve the pathname through the source
code so that chdir() maybe called instead. This is the typical
workaround. Often a global variable will be used specifically for
this purpose and access to the variable may be guarded by locks if
used in more than one thread.