Use / path separator on Windows in export dialog

src/imageio/storage/disk.c

@@ -223,8 +223,9 @@ static void button_clicked(GtkWidget *widget,
 
     // composed can now contain '\': on Windows it's the path separator,
     // on other platforms it can be part of a regular folder name.
-    // This would later clash with variable substitution, so we have to escape them
-    gchar *escaped = dt_util_str_replace(composed, "\\", "\\\\");
+    // This would later clash with variable substitution.
+    // For now, let's use Linux '/' separator, as it also works on Windows.
+    gchar *escaped = dt_util_str_replace(composed, "\\", "/");
 
     gtk_entry_set_text(GTK_ENTRY(d->entry), escaped);
     // the signal handler will write this to conf