gnu: julius: Remove unused bundled libraries.

* gnu/packages/games.scm (julius)[source](snippet): Remove
ext/{dirent,png,SDL2,zlib}.

Signed-off-by: Nicolas Goaziou <mail@nicolasgoaziou.fr>

gnu/packages/games.scm

@@ -987,7 +987,14 @@ (define-public julius
              (commit (string-append "v" version))))
        (file-name (git-file-name name version))
        (sha256
-        (base32 "01rygr592ar530qv1flmaiq8icl0qdxgc8lhkcdyn1g09941z47v"))))
+        (base32 "01rygr592ar530qv1flmaiq8icl0qdxgc8lhkcdyn1g09941z47v"))
+       ;; Remove unused bundled libraries.
+       (modules '((guix build utils)))
+       (snippet
+        '(begin
+           (with-directory-excursion "ext"
+             (for-each delete-file-recursively '("dirent" "png" "SDL2" "zlib")))
+           #t))))
     (build-system cmake-build-system)
     (inputs
      `(("libpng" ,libpng)
@@ -1001,7 +1008,6 @@ (define-public julius
 bugs) of the original game, so that saved games are compatible.  This package
 does not include game data.")
     (license (list license:agpl3
-                   license:expat        ; ext/dirent
                    license:zlib))))     ; ext/tinyfiledialogs
 
 (define-public meandmyshadow