Disable OpenMP offloading support for 3rdparty/openmp

OpenMP offloading was introduced some time during the past two years and is
enabled by default. With upgrading 3rdparty/openmp in
apache#17012
it was made part of the MXNet CMake build.

But we don't use OpenMP offloading and the Cuda target in the llvm OpenMP
Offloading build is broken in our setting.

CMakeLists.txt

@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.0.2)
+cmake_minimum_required(VERSION 3.13)
 
 # workaround to store CMAKE_CROSSCOMPILING because is getting reset by the project command
 if(CMAKE_CROSSCOMPILING)
@@ -453,6 +453,7 @@ if(USE_OPENMP)
  set(LIBOMP_ENABLE_SHARED TRUE)
  set(CMAKE_BUILD_TYPE Release)
  add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/3rdparty/openmp)
+ set(OPENMP_ENABLE_LIBOMPTARGET OFF CACHE BOOL "LLVM OpenMP offloading support") # Requires CMP0077 CMake 3.13
  endfunction()
 
  find_package(OpenMP REQUIRED)