Fix leak in truffleposix_get_user_home

Author: chrisseaton

src/main/c/truffleposix/truffleposix.c

@@ -202,6 +202,7 @@ char* truffleposix_get_user_home(const char *name) {
     return NULL;
   } else {
     /* ret == 0 && result == NULL means not found */
+    free(buffer);
     return strdup("");
   }
 }