A mac is required in the build chain, because only a mac can run Xcode. The IDE sends your code to a mac over the network to be compiled by Xcode. If you don't have a mac, you can use a remote "hosted builder" for a small fee. If you do own a mac, you can build locally.
I have a mac and run the IDE in a windows VirtualBox. I rarely ever have to touch the mac side of things to build apps, as the local builder software operates as a server.