This fixes compilation of wxGTK under Windows after the changes of r72779 and
r72780, where _wchdir() would need to be used but we don't currently have a
wxChdir() CRT function wrapper so use wxSetWorkingDirectory() instead.
Closes#14886.
git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73160 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775