The following can be built with --build always being
equal to x86_64-unknown-linux-gnu and --host always
being equal to what uname -m gives.

Build order:

01. Build GMP
02. Build MPFR
03. MPC
04. binutils
05. libelf
06. core pass 1 compiler (doesn't need libc, can setup libc)
07. kernel headers
08. C library headers and start files
09. core pass 2 compiler
10. complete C library (multilib)
11. final compiler (multilib)