version is empty when invoking https-dns-proxy -V on OpenWrt

Hello,

Is the version information present on a normal Linux distro? On OpenWrt, I get:

```sh
SG-135 in ~ # https-dns-proxy -V

SG-135 in ~ #
```

Do I need to pass something as a CMAKE_OPTIONS in the [Makefile](https://github.com/openwrt/packages/blob/master/net/https-dns-proxy/Makefile) to have it print a valid version information?

Thanks!