ext,test: Provide default terminal size

ext,test: Provide default terminal size

When creating the separator for printing things to the terminal (=.*) we
use an ioctl that isn't supported in some sandboxed environments. When
running on the Google jenkins server (kokoro) it errors with an IOError.

Change-Id: I148dd87cffe6e93d6723a386aecf9a9ea6c5b455
Signed-off-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/17449
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>