Fix support for non-EXE executables for archver commands.

[John Small]

The help screen for the "Edit an archiver" dialog suggests that non-EXE programs (CMD, BAT, COM, BTM) may be used.

There is also code in NornmalizeCmdLine (pathutil.c) which seems to provide support for these alternative program extensions.

But something, somewhere is broken because the edits complain about anything but an EXE program.