[Sim] New sim/common/cgen.sh

[Doug Evans]

Ben Elliston writes:
 >       Also, while the existing script has problems with parallel makes, your
 >       version has even worse problems.  You might want to fix that.
 > 
 > I have also just fixed genmloop.sh so that it has an -outfile-suffix option.
 > This allows the generated files to form unique filenames -- so it, too, can
 > be run by a parallel make.

Can't this problem be solved without adding an option?