Add dummy tool "calculatepi" that can be used as a simple CPU benchmark.
Add dummy tool "calculatepi" that can be used as a simple CPU benchmark.

martin-neuhaeusser/benchexec,ultimate-pa/benchexec,IljaZakharov/benchexec,martin-neuhaeusser/benchexec,dbeyer/benchexec,ultimate-pa/benchexec,martin-neuhaeusser/benchexec,dbeyer/benchexec,IljaZakharov/benchexec,dbeyer/benchexec,sosy-lab/benchexec,ultimate-pa/benchexec,ultimate-pa/benchexec,sosy-lab/benchexec,ultimate-pa/benchexec,IljaZakharov/benchexec,sosy-lab/benchexec,sosy-lab/benchexec,sosy-lab/benchexec,martin-neuhaeusser/benchexec,dbeyer/benchexec,ultimate-pa/benchexec,sosy-lab/benchexec,IljaZakharov/benchexec