Invert conditions so that an empty codetaskassembly causes the use of compiled tasks
Invert conditions so that an empty codetaskassembly causes the use of compiled tasks

Since the first UsingTask to appear wins, an overriding condition for UseCompiledTasks=false
won't take precedence over an empty CodeTaskAssembly, which would make it impossible to use
anyway.

MobileEssentials/MSBuilder,kzu/MSBuilder,adalon/MSBuilder