Got cmake working on linux

There are lots of vars to set. For reference, the command I use is:

cmake -D LLVM_BIN=~/projects/Halide/llvm/trunk/build-64/bin/ -D LLVM_LIB=~/projects/Halide/llvm/trunk/build-64/lib/ -D LLVM_INCLUDE=~/projects/Halide/llvm/trunk/include/ -D LLVM_VERSION=35 -D LLVM_ENABLE_TERMINFO=OFF -D LLVM_TARGETS_TO_BUILD='X86;ARM;NVPTX;AArch64' -D LLVM_ENABLE_ASSERTIONS=ON -D CMAKE_BUILD_TYPE=Release -D CMAKE_CXX_COMPILER=/usr/local/bin/g++ -D CMAKE_C_COMPILER=/usr/local/bin/gcc -D LLVM_CONFIG=~/projects/Halide/llvm/trunk/build-64/bin/llvm-config -D TARGET_NATIVE_CLIENT=OFF ..