* Check out the sources:

mkdir src
cd src
svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm
cd llvm/tools
svn co http://llvm.org/svn/llvm-project/cfe/trunk clang
svn co http://root.cern.ch/svn/root/trunk/cint/cling cling
cd ..

* Apply some patches

cat tools/cling/patches/* | patch -p0

* Configure, build and install them

cd ..
mkdir build
cd build
../llvm/configure --enable-targets=host
make
make install