This allows users to see progress whenever the docker image is
[re]built, and (esp on non-linux hosts) track the size of the build
context being uploaded. Currently no output is displayed, so it's hard
to attribute the source of latency, e.g. network latency, building
layers, a large work directory, etc.
Now that we have a base docker image that has all our RPC compilation
dependencies installed, we can also run the mobile RPC compilation
there. This removes the need to install falafel and goimports on the
local machine.
This commit aims to make it easier for developers to compile our
protobuf definitions. They now only need to have docker installed
instead of a whole set of binaries and libraries all pinned to very
specific versions.