Update rapids-cmake to 21.12 (#1931)

Required to merge rapidsai/raft#370

Authors:
  - Dante Gama Dessavre (https://github.com/dantegd)

Approvers:
  - Chuck Hastings (https://github.com/ChuckHastings)

URL: #1931

cpp/CMakeLists.txt

@@ -15,7 +15,7 @@
 #=============================================================================
 
 cmake_minimum_required(VERSION 3.20.1 FATAL_ERROR)
-file(DOWNLOAD https://raw.githubusercontent.com/rapidsai/rapids-cmake/branch-21.10/RAPIDS.cmake
+file(DOWNLOAD https://raw.githubusercontent.com/rapidsai/rapids-cmake/branch-21.12/RAPIDS.cmake
     ${CMAKE_BINARY_DIR}/RAPIDS.cmake)
 include(${CMAKE_BINARY_DIR}/RAPIDS.cmake)