Remove legacy build directory caching
In !1319 (merged) we added back the old way of how we cache the build directory for Docker since it cases regressions like #4174 (closed). However, the old behavior is incorrect and we should remove this earlier then %13.0 becuase %13.0 is a little long (1 year from now as of the time of writing)
- %11.11 Update the feature flag documentation to specify %12.3
%11.11%12.0 release post announces that this is going to change.
In %12.0 update documentation educating users that they should never us
build_dirfor their own stuff, but should always be outside of that directory #4436 (closed)
- In %12.3 remove the whole thing