Use gc_strdup

git-svn-id: https://svn.parrot.org/parrot/branches/boehm_gc_2@44405 d31e2699-5ff4-0310-a27c-f18f2fbe73fe

src/library.c

@@ -813,7 +813,7 @@ Parrot_get_runtime_prefix(PARROT_INTERP)
             return Parrot_str_to_cstring(interp, s);
         }
         else
-            return mem_sys_strdup(".");
+            return Parrot_gc_strdup(interp, ".");
     }
 }