curl -s https://github.com/matthiasr/summon-arm-toolchain/raw/master/summon-arm-toolchain | /bin/sh
git clone git://github.com/matthiasr/r0ket.git r0ket
cd r0ket/firmware
cp SECRETS SECRETS.release
PATH=$HOME/arm/bin:$PATH ./release-all

I adapted a Script for building a GNU binutils/GCC/Newlib/GDB toolchain. It should be portable. gmp, mpfr and mpc need not be installed.

The script will build binutils, gcc, the newlib C library, gcc again and gdb into ~/arm by default.

Currently there is one issue with the mainline r0ket firmware; in some circumstances the linker for loadables fails to find some library functions gcc inserts on variable initialisations or something. I've found that linking with gcc instead fixes this problem. A fixed version is available from my repo for now.