compile llvm and clang with some nice backends and tools

Compile llvm and clang

# Get llvm
svn co http://llvm.org/svn/llvm-project/llvm/tags/RELEASE_370/final/ llvm

# Get clang
cd llvm/tools
svn co http://llvm.org/svn/llvm-project/cfe/tags/RELEASE_370/final/ clang

#Checkout Compiler-RT (required to build the sanitizers) [Optional]:
cd ../projects
svn co http://llvm.org/svn/llvm-project/compiler-rt/tags/RELEASE_370/final/ compiler-rt

# Checkout Libomp (required for OpenMP support) [Optional]:
cd ../projects
svn co http://llvm.org/svn/llvm-project/openmp/tags/RELEASE_370/final/ openmp

# Checkout libcxx and libcxxabi [Optional]:
cd ../projects
svn co http://llvm.org/svn/llvm-project/libcxx/tags/RELEASE_370/final/ libcxx
svn co http://llvm.org/svn/llvm-project/libcxxabi/tags/RELEASE_370/final/ libcxxabi

# Checkout resurrected LLVM "C Backend"
cd ../projects
git clone https://github.com/JuliaComputing/llvm-cbe.git llvm-cbe

# Create build directory
cd ..
mkdir build
cd build
# Generate makefiles
cmake -G "Unix Makefiles" -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=prefix=/usr -DLLVM_TARGETS_TO_BUILD="AArch64;AMDGPU;ARM;CppBackend;X86" ../
# Build
make