Add relative package path support to iree_cc_test.cmake
Add relative package path support to iree_cc_test.cmake

Matches the behavior of iree_cc_library and iree_cc_binary added in https://github.com/google/iree/pull/608

Closes https://github.com/google/iree/pull/645

COPYBARA_INTEGRATE_REVIEW=https://github.com/google/iree/pull/645 from GMNGeoffrey:cmake-cc-test 1595664ad3e0ce0128e8593b10ccec92860f108d
PiperOrigin-RevId: 292718854

google/iree,iree-org/iree,google/iree,google/iree,google/iree,iree-org/iree,iree-org/iree,iree-org/iree,google/iree,iree-org/iree,google/iree,iree-org/iree,google/iree,iree-org/iree