Please, eliminate workspace layout requirements to build the IGC. As of now you require the following folder structure:

workspace
      |- clang_source           https://github.com/llvm-mirror/clang
      |- common_clang           https://github.com/intel/opencl-clang
      |- llvm_patches           https://github.com/intel/llvm-patches
      |- llvm_source            https://github.com/llvm-mirror/llvm
      |- igc                    https://github.com/intel/intel-graphics-compiler
      |- opencl_headers         https://github.com/KhronosGroup/OpenCL-Headers

Please, remove this completely. It is expected that project will require steps similar to the following to build:

git clone https://github.com/intel/intel-graphics-compiler.git && cd intel-graphics-compiler
mkdir build && cd build
cmake ..
make -j8
make install

There are the following options to consider dealing with dependencies:

1. Detect dependencies installed on the system via pkg-config and other standard tools. Error out if dependency is not satisfied: that's an end-user responsibility to satisfy the dependency.
2. Pull in sources of the dependency inside your project via: 1) just copy - that's the usual case for gtest, your opencl headers is the obvious candidate, 2) use git submodule.