Change the CMake version to 3.15

CMake 3.15 or greater is required for gRPC

Change-Id: I15cda7b2bccb2bc1c46b3bb84eb1116a15ce32a4

CMakeLists.txt

@@ -21,7 +21,7 @@
 #
 # Minimum version of cmake required
 #
-cmake_minimum_required(VERSION 3.5.0)
+cmake_minimum_required(VERSION 3.15)
 
 # ROCM_DIR should be passed in via command line; these will be used
 # in sub-projects