A construction guy named Omar in Austin, Texas, became an “Instagram influencer” recently after attracting hundreds of thousands of followers to his @justaconstructionguy account with just a handful of photos. But it turns out the guy was a carefully crafted persona designed to help a small coffee shop sell coffee. After being created in May, the account shot to Insta-stardom when it was Tweeted out by Twitter user @barbzlovescarbs, who purported to be Omar’s daughter. In his photos and captions,…