vsh: Fix broken build on mingw

The function wcwidth() doesn't exist on mingw. However, it does exist in
gnulib, so we can rely on that.

Signed-off-by: Simon Kobyda <skobyda@redhat.com>
Reviewed-by: Erik Skultety <eskultet@redhat.com>

bootstrap.conf

@@ -126,6 +126,7 @@ vc-list-files
 vsnprintf
 waitpid
 warnings
+wcwidth
 '
 
 SKIP_PO=true