build: Fix installing vkd3d-proton when Wine is built without vkd3d

This would fail previously as Wine does not have d3d12.dll for us to make .old

Closes: #559
Signed-off-by: Joshua Ashton <joshua@froggi.es>

setup_vkd3d_proton.sh

@@ -120,11 +120,10 @@ installFile() {
       else
         rm -v "${dstfile}"
       fi
-      $file_cmd "${srcfile}" "${dstfile}"
     else
-      echo "${dstfile}: File not found in wine prefix" >&2
-      return 1
+      touch "${dstfile}.old_none"
     fi
+    $file_cmd "${srcfile}" "${dstfile}"
   fi
   return 0
 }
@@ -148,6 +147,10 @@ uninstallFile() {
     rm -v "${dstfile}"
     mv -v "${dstfile}.old" "${dstfile}"
     return 0
+  elif [ -f "${dstfile}.old_none" ]; then
+    rm -v "${dstfile}.old_none"
+    rm -v "${dstfile}"
+    return 0
   else
     return 1
   fi