fixup ttcn3-tcpdump-stop.sh: add flag '--force' to gzip

When a directory path for the "build artifacts" is not specified,
'/tmp' would be used by default.  When running the same text
case more than once, gzip will be asking for confirmation whether
to overwrite the existing capture file.  Let's do this by default.

Change-Id: I357f3d9c5dc5963f4b709166bb659f3f66a721b8
1 file changed