cmake ILMBASE_HAVE_PTHREAD examples

UPBGE/upbge build_files/build_environment/patches/cmake/modules/FindIlmBase.cmake :229

file(STRINGS ${ILMBASE_INCLUDE_DIR}/OpenEXR/IlmBaseConfig.h
    ILMBASE_HAVE_PTHREAD
    REGEX "^[ \\t]*#define[ \\t]+HAVE_PTHREAD[ \\t]1[ \\t]*\$"
  )