LibC: Missing varargs cleanup in fcntl

Author: https://github.com/bgianfo
Commit: dc278c3aa1
Pull-request: https://github.com/SerenityOS/serenity/pull/3184
Reviewed-by: https://github.com/awesomekling
Reviewed-by: https://github.com/bugaevc

Libraries/LibC/fcntl.cpp

@@ -38,6 +38,7 @@ int fcntl(int fd, int cmd, ...)
     va_start(ap, cmd);
     u32 extra_arg = va_arg(ap, u32);
     int rc = syscall(SC_fcntl, fd, cmd, extra_arg);
+    va_end(ap);
     __RETURN_WITH_ERRNO(rc, rc, -1);
 }