lang/intel-compute-runtime: enable debug variables

$ clinfo | fgrep 'Platform Version'

Platform Version                                OpenCL 3.0

$ ForceOCLVersion=12 clinfo | fgrep 'Platform Version'

Platform Version                                OpenCL 1.2

https://github.com/intel/compute-runtime/blob/21.26.20194/shared/source/debug_settings/debug_variables_base.inl
(cherry picked from commit 83ca5042280797b5622e1202df90c9c1d36356bd)