To build, you must have a minimal cross-compiler for x86_64-elf. Follow the
directions at http://wiki.osdev.org/GCC_Cross-Compiler for target x86_64-elf to set
one up, and make sure it is in your path. When you are set up make should be
sufficient.
To run, execute:
./script/QEMU.sh userland/calc.bin
If you want to try GDB debugging, run:
./script/QEMU.sh -S userland/calc.bin
And then in a separate terminal, attach with:
./script/GDB.sh
Or whatever other userland program(s) you would like.