gnu: qtimageformats: Remove bundled libraries.

* gnu/packages/qt.scm (qtimagesformats)[source]: Remove bundled 3rd
party libraries.

gnu/packages/qt.scm

@@ -541,7 +541,11 @@ (define-public qtimageformats
                                  version ".tar.xz"))
              (sha256
               (base32
-               "1rb27x7i2pmvsck6wax2cg31gqpzaakciy45wm5l3lcl86j48czg"))))
+               "1rb27x7i2pmvsck6wax2cg31gqpzaakciy45wm5l3lcl86j48czg"))
+             (modules '((guix build utils)))
+             (snippet
+              '(begin
+                 (delete-file-recursively "src/3rdparty")))))
     (native-inputs `())
     (inputs
      `(("libmng" ,libmng)