Add some very simple integration tests to BenchExec.
Add some very simple integration tests to BenchExec.

sosy-lab/benchexec,cheshire/benchexec,IljaZakharov/benchexec,dbeyer/benchexec,bjowac/impara-benchexec,sosy-lab/benchexec,martin-neuhaeusser/benchexec,bjowac/impara-benchexec,michkot/benchexec,ultimate-pa/benchexec,dbeyer/benchexec,ultimate-pa/benchexec,sosy-lab/benchexec,sosy-lab/benchexec,IljaZakharov/benchexec,sosy-lab/benchexec,michkot/benchexec,bjowac/impara-benchexec,dbeyer/benchexec,IljaZakharov/benchexec,martin-neuhaeusser/benchexec,ultimate-pa/benchexec,martin-neuhaeusser/benchexec,sosy-lab/benchexec,cheshire/benchexec,dbeyer/benchexec,michkot/benchexec,ultimate-pa/benchexec,ultimate-pa/benchexec,IljaZakharov/benchexec,ultimate-pa/benchexec,martin-neuhaeusser/benchexec,cheshire/benchexec