Fix: proxy & ninja issue

[yxKryptonite]

• depot_tools needs VPN to access in mainland China, while the code doesn't provide the option to use same proxy in docker as the host, so I add the feature to configure the proxy port in docker and use the same network environment as the host.

• In the recent update, depot_tools doesn't include ninja, so you should install ninja in docker manually. And I wrote it in the dockerfile.