dxvk: fix DLL override setup

`basename srcpath` simply prints "srcpath" which results in a single DLL
override for srcpath.dll to be installed... clearly not what we want.

pkgs/misc/dxvk/setup_dxvk.sh

@@ -261,5 +261,5 @@ done
 
 for srcpath in "${!paths[@]}"; do
     ${action}_file "$srcpath" "${paths["$srcpath"]}"
-    ${action}_override "$(basename srcpath)"
+    ${action}_override "$(basename "$srcpath" .dll)"
 done