Add make.out to gitignore file.

It's produced by "make simple-test" in testrunner directory.

Change-Id: I9f7e313c5dfe31ea86890bd38a036c768de3d16c
Reviewed-on: http://review.couchbase.org/37514
Tested-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>