demo: investigate unity cloud build infrastructure value

[reinterpretcat]

travis ci provides the easy way to test core logic, but unity specific logic is not covered. Need to check whether unity cloud build can help to build set of smoke tests.

[reinterpretcat]

observed problem with dependencies (plugins): they are not committed. In general, idea is to use simple script with UNITY_CLOUD_BUILD symbols which would download utymap's shared and unity libs and copy them to plugin folder. Unity provides post build check, but seems there is no good way to execute logic before builds is started.