first of all:
Both of you turned up at about the same time with about the same question .. Are you the same person/working together? Can I ask where and how you learned about RIOT?
Regarding booting RIOT: - RIOT is generally targeting microcontroller IoT hardware, not PC hardware - when compiling RIOT you have various target choices, among them are two virtual platforms, namely 'native' and 'qemu-i386' - 'native' is a virtual platform meant for testing and debugging of RIOT and RIOT applications, 'qemu-i386' is more or less a proof of concept - you can run RIOT on QEMU (see below) when compiling for the 'qemu-i386' target, but there is no way to run the binary compiled for 'native' on 'qemu-i386'
Two things to keep in mind: - support for QEMU is rather rudimentary, for example there is no network - running RIOT as an OS on a desktop PC (instead of OSX, Windows or Linux) is not intended, nor is it possible at the moment
The big question: - Why do you want to run the application on QEMU? What are you trying to achieve by running it on that platform?
Compiling and running on 'qemu-i386': BOARD=qemu-i386 make clean all flash term
The same applies for all other platforms. To compile for, flash to, and test on real hardware like the 'samr21-xpro': BOARD=samr21-xpro make clean all flash term