Trunk broken on MS-Windows

[Eli Zaretskii]

The build fails with these error messages:

  Warning: arch-independent data dir `%emacs_dir%/share/emacs/25.0.50/etc/': 
Permission denied
  Warning: Lisp directory `./lisp': No such file or directory
  Error: charsets directory not found:
  d:/gnu/bzr/emacs/trunk/src/%emacs_dir%/share/emacs/25.0.50/etc/charsets
  Emacs will not function correctly without the character map files.
  Please check your installation!
  Makefile:833: recipe for target `bootstrap-emacs.exe' failed
  make[1]: *** [bootstrap-emacs.exe] Error 1

Looks like some fallout from commits in r118316..118318.