I'm willing to bet iOS has a huge build infrastructure, many different components, and about a snowball's chance in hell of having a single nice clean Makefile for you to type one command to get a build without access to that infrastructure.
But the point is that Apple has that infrastructure. If the FBI asked the right person or people, I would bet they could get this done on their lunch break.
People are making it out like the FBI is asking Apple to rewrite a big part of iOS. That's not the part of the request that's the problem.
I'm willing to bet iOS has a huge build infrastructure, many different components, and about a snowball's chance in hell of having a single nice clean Makefile for you to type one command to get a build without access to that infrastructure.