Fix the option to pipe stdin to the compiler.

[fruffy]

This option was never working because - was interpreted as a flag parameter. This little change fixes that. Now it is possible to directly pipe a program to the compiler instead of reading a file.

Open to suggestions on how to improve this option. The parser options in general are old and quite messy.

[smolkaj]

What would be a concrete example of a command that didn't work before but works now?

[fruffy]

What would be a concrete example of a command that didn't work before but works now?

Before:

echo "control dummy();" | p4c/build/p4test -
[--Werror=unknown] error: Unknown option -                                                                 

After:

echo "control dummy();" | p4c/build/p4test -
[--Wwarn=missing] warning: Program does not contain a `main' module

[smolkaj]

Thanks, I understand better now.
Perhaps worth adding a quick comment in the code about it?

[smolkaj]

Sweet!

[jafingerhut]

LGTM