A build was hanging with `UBUNTU_VERSION=20.04`
```
...
=> [base 3/5] RUN APT-GET update && apt-get install -y dpkg-dev git make pkg-config 73.2s
=> => # questions will narrow this down by presenting a list of cities, representing
=> => # the time zones in which they are located.
=> => # 1. Africa 4. Australia 7. Atlantic 10. Pacific 13. Etc
=> => # 2. America 5. Arctic 8. Europe 11. SystemV
=> => # 3. Antarctica 6. Asia 9. Indian 12. US
=> => # Geographic area:
...
```
Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>
d1e1a16460