This patch updates `Build.mak` to ensure that unittests and integration
tests will always be run for all of the supported engine types.  As well
as making it easier to run tests for all engines locally, this will make
it possible to greatly simplify our CI setup.

Since `Build.mak` now takes care of running tests with all engines, we
can greatly simplify the number and configuration of Travis CI jobs.
This patch reduces the setup to cover development and production builds
for D1 and D2 respectively.

… types

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This should get the dependencies working OK.