Fix name of C-Ares source directory & make the name of the -done file match it.

The directory's name begins with "c-ares-", not "cares-".  Fix that, and
make the -done file's name begin with "c-ares-" as well.

Change-Id: Ifa178c638ca634ca6b762b12290ccfcc4fa928f9
Reviewed-on: https://code.wireshark.org/review/5015
Reviewed-by: Guy Harris <guy@alum.mit.edu>