ttasim fails to simulate operations in case fails to rebuild .opb

[Pekka Jääskeläinen]

ttasim now rebuilds .opb on the fly (at least when it cannot simulate an operation) and when it fails to build it (e.g. a missing LDFLAG) it complains that it fails to simulate any operation coming from that same operation module (.opp). The fix here would be to print out a more descriptive error message that prints out the operations that cannot be simulated.

Steps to reproduce:
- define an operation module with at least one without a simulation function or OperationDAG
- another with an OperationDAG

Try to load a program using that in ttasim. It complains about all of the operations.