To run the 2.2 conformance tests test suite for the C++ features you need
SPIR-V binaries.

If you are using a conformance package then the binaries are included in the 
package. If you are using conformance tests from git repositories then the
binaries need to be picked up using LFS:

1. Setup LFS by following instructions at https://git-lfs.github.com/

2. The SPIR-V binaries can then be picked up from test_conformance/clcpp/spirv*.7z

Alternatively you can check out and build all of the below repositories
manually or use https://github.com/KhronosGroup/OpenCL-CTS-Framework which will
do it for you.

1. SPIRV-LLVM
LLVM with support for SPIR-V (required by clang compiler)
Repository: https://gitlab.khronos.org/opencl/SPIRV-LLVM
Branch: spec_constants 
Notes: spirv-3.6.1 is a main branch with support for OpenCL C++ kernel language,
  spec_constants is based on it, but it adds support for specialization constants.

2. Clang 
Clang with support for OpenCL C++ kernel language
Repository: https://gitlab.khronos.org/opencl/clang
Branch: spec_constants 
Notes: spirv-1.1 is a main branch with support for OpenCL C++ kernel language, 
  spec_constants is based on it, but it adds support for specialization constants.

3. libclcxx
OpenCL C++ Standard Library
Repository: https://gitlab.khronos.org/opencl/libclcxx 
Branch: lit_tests_cl22   
Notes: lit_tests_cl22 branch includes both LIT tests and changes introduced in 
  spec_constants branch, that is, implementation of Specialization Constants Library.   

4. OpenCL 2.2 headers
OpenCL 2.2 headers
Repository: https://gitlab.khronos.org/opencl/headers 
Branch: opencl22 

5. OpenCL ICD (with 2.2 support)
OpenCL ICD 
Repository: https://gitlab.khronos.org/opencl/icd 
Branch: dev_cl22