Reduce minimum CMake version
Summary:
PyTorch's open-source CI environment has CMake 3.5.1.  Looking at the
release notes, there's nothing obvious in 3.6 that we need, especially
with fbjni tests disabled.
Pull Request resolved:
# See the License for the specific language governing permissions and
# limitations under the License.
-cmake_minimum_required(VERSION 3.6.0)
+cmake_minimum_required(VERSION 3.5.0)
project(fbjni CXX)
set(FBJNI_COMPILE_OPTIONS
