[OpenMP][omptest] Fix CMake target properties (#176802) Fix visibility of target properties: * INCLUDE_DIRECTORIES * COMPILE_DEFINITIONS implicitly pulled in from `default_gtest`. Fixes: https://github.com/llvm/llvm-project/pull/159416 GitOrigin-RevId: 696b91aeb7e55d5fbc82b2e6a625f2a7ca4a6911