Install some needed libraries

sudo aptitude install libmpc-dev

Make the temp directory to build in

mkdir toolchain
cd toolchain

Get the required sources

wget -c ftp://sources.redhat.com/pub/newlib/newlib-1.19.0.tar.gz
wget -c http://ftp.gnu.org/gnu/gdb/gdb-7.2.tar.gz
wget -c http://ftp.gnu.org/gnu/binutils/binutils-2.21.tar.bz2
wget -c http://ftp.gnu.org/gnu/gcc/gcc-4.6.0/gcc-core-4.6.0.tar.bz2
wget -c http://ftp.gnu.org/gnu/gcc/gcc-4.6.0/gcc-g++-4.6.0.tar.bz2

tar -xvf binutils-2.21.tar.bz2
tar -xvf gcc-core-4.6.0.tar.bz2
tar -xvf newlib-1.19.0.tar.gz
tar -xvf gdb-7.2.tar.gz
tar -xvf gcc-g++-4.6.0.tar.bz2

Set up the required variables

export target=arm-eabi
export prefix=/usr/local/$target
export PATH=$prefix/bin:$PATH

Create the bin folder for the final binaries

sodo mkdir -p $prefix/bin

Build binutils

cd binutils-2.21
mkdir build-$target
cd build-$target
../configure --target=$target --prefix=$prefix\
    --enable-interwork --enable-multilib --disable-werror
make
sudo make install

Build the temporary gcc to build newlib with. Make sure the --with-headers line references the version of newlib you downloaded

cd ../../gcc-4.6.0
mkdir build-$target
cd build-$target
../configure --target=$target --prefix=$prefix \
    --enable-languages=c,c++ --enable-interwork \
    --enable-multilib --with-dwarf2 --with-newlib \
    --with-headers=../../newlib-1.19.0/newlib/libc/include
make all-gcc
sudo make install-gcc

Build newlib

cd ../../newlib-1.19.0
mkdir build-$target
cd build-$target
../configure --target=$target --prefix=$prefix --enable-interwork --enable-multilib
make
sudo make install

Build the final gcc

cd ../../gcc-4.6.0/build-$target
make
sudo make install

Build gdb

cd ../../gdb-7.2
mkdir build-$target
cd build-$target
../configure --target=$target --prefix=$prefix
make
sudo make install

Originally blatantly stolen from the Ethernut Project, just documenting my experience with it on a 10.6 Macbook Air with the newest versions of each tool. Since then it has been updated to build the newer eabi target instead of elf.

If you get errors to do with warnings being treated as errors you can use --disable-werror at any of the build steps.