Add sollve_vv external project.

sollve_vv is the OpenMP Validation & Verification suite to test
conformance to with the OpenMP specification.

It is included as an external project, i.e. some work is required before
it is enabled, for instance setting TEST_SUITE_SOLLVEVV_ROOT to the
downloaded source repository. OpenMP is detected using CMake's
find_package(OpenMP) but the offloading flags must be specified manually
in CMake using TEST_SUITE_SOLLVEVV_OFFLOADING_CFLAGS and
TEST_SUITE_SOLLVEVV_OFFLOADING_LDFLAGS.

Differential Revision: https://reviews.llvm.org/D70065
4 files changed