Below are the steps to reproduce:

Step 1
------
Download the openembedded image and resize it by adding ~10GB. 

Steps to do that is described here.
https://wiki.linaro.org/WorkingGroups/ToolChain/IncreaseImageSize

I used latest image "vexpress64-openembedded_lamp-armv8_20130526-344.img" at http://www.linaro.org/engineering/armv8

Step 2
------ 
Check out GCC trunk
svn checkout svn://gcc.gnu.org/svn/gcc/trunk gcc199474

I used trunk revision 199474

Step 3
------
Mount and copy GCC source to /home/root

sudo mount -o loop,offset=54525952 -t ext4
vexpress64-openembedded_lamp-armv8_20130526-344.img  /mnt/temp2

copy the source to /mnt/temp2/home/root

Step 4
------
Start the V8 model and boot openembedded image

./Foundation_v8pkg/Foundation_v8 --image img-foundation.axf
--block-device vexpress64-openembedded_lamp-armv8_20130526-344.img
--network=nat --network-nat-ports=8022=22

Step 5
-------
In the xterm window go to /home/root, create a build directory, configure and run make.

mkdir build
cd build
../gcc199474/configure  --enable-languages=c,c++ --disable-threads
--disable-libssp --disable-libgomp --disable-libmudflap
--disable-libatomic --without-libquadmath --disable-libquadmath
--prefix=/home/root/install
make