Changes:
- replaced registry keys with environment variables
for cl_cache in OCL
- added compiler cache helpers
- implemented support for new env vars on Windows
- added tests
New env vars mechanism works as follows:
If `PERSISTENT_CACHE` is set,
driver checks if `NEO_CACHE_DIR` is set.
If `NEO_CACHE_DIR` is not set,
driver uses `%LocalAppData%\NEO\neo_compiler_cache`
as `cl_cache` destination folder.
If `NEO_CACHE_DIR` is not set and `%LocalAppData%`
path could not be obtained,
compiler cache is disabled.
In the current Windows implementation,
special characters in the folder path are not supported.
Related-To: NEO-8092
Signed-off-by: Fabian Zwolinski <fabian.zwolinski@intel.com>
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