Build failure on building inline client + server version

[mschweiger]

Intermittently a build fails because the inline client and server versions both write files to the same directory, causing a race condition.

It appears that the orbiter.lib and orbiter.exp files are written to the intermediate build directory (Src\Orbiter) even if the corresponding ENABLE_EXPORTS flag is not set. This means that both the orbiter inline client and server builds try to write and access the same files, causing build failures.

Solution: make one of the builds dependent on the other, to disable concurrent builds, and explicitly delete orbiter.lib and orbiter.exp between the two runs.