Fix an issue with leiningen's tests on Windows.

Deleting one of the jar files in the sample test project
was failing on Windows, which was causing all sorts of hard to debug
test errors.

Calling System/gc seems to do the trick (at least on Vista),
but it is not really a proper solution.
If anybody has a better idea, please speak up.

test/leiningen/test/deps.clj

@@ -50,7 +50,12 @@
       (let [rel-repo-snaps-dep (assoc pr :dependencies [clj-time])]
         (is (thrown? Exception (with-no-log (deps rel-repo-snaps-dep))))))
     (finally
-       (delete-file-recursively (file (:root sample-project) "lib")))))
+     ;; Without triggering the GC, joda jar cannot be deleted on
+     ;; Windows, which causes all sorts of seemingly unrelated test
+     ;; failures. If anybody knows how to fix this properly, please do
+     ;; it.
+     (System/gc)
+     (delete-file-recursively (file (:root sample-project) "lib")))))
 
 (deftest test-native-deps
   (delete-file-recursively (:library-path native-project) true)