http://blog.darkhax.com/2009/06/24/compile-llvm-on-ubuntu

output.txt

Using built-in specs.
Target: i686-pc-linux-gnu
Configured with: ./configure --prefix=/home/darkhelmet/local/llvm-gcc --enable-languages=c,c++ --program-prefix=llvm- --enable-llvm=/home/darkhelmet/local/llvm
Thread model: posix
gcc version 4.2.1 (Based on Apple Inc. build 5636) (LLVM build)

setup.sh

cd; mkdir llvm; cd llvm
unset LD_LIBRARY_PATH
unset LIBRARY_PATH
unset C_INCLUDE_PATH
wget http://llvm.org/releases/2.5/llvm-gcc-4.2-2.5.source.tar.gz
wget http://llvm.org/releases/2.5/llvm-2.5.tar.gz
tar zxf llvm-2.5.tar.gz
tar zxf llvm-gcc-4.2-2.5.source.tar.gz
cd llvm-2.5
./configure --prefix=$HOME/local/llvm --enable-pic
make -j3 # alter to suite your system, usually 1 + number of cores
make install
cd ../llvm-gcc4.2-2.5.source
./configure --prefix=$HOME/local/llvm-gcc --enable-languages=c,c++ --program-prefix=llvm- --enable-llvm=$HOME/local/llvm
make -j3 all
make install
cd ~/local/llvm-gcc/bin
./llvm-gcc -v