CCBC-548 Check if snappy enabled when generating dummy source target

Change-Id: I2341f9fae8918629182cfba0ec1a0d7e7a22dd69
Reviewed-on: http://review.couchbase.org/43042
Tested-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Reviewed-by: Mark Nunberg <mnunberg@haskalah.org>