[CMake] Bump CMake version required 3.14 -> 3.20

This matches the required version for llvm-project.

Author: RossBrunton

CMakeLists.txt

@@ -3,7 +3,7 @@
 # See LICENSE.TXT
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-cmake_minimum_required(VERSION 3.14.0 FATAL_ERROR)
+cmake_minimum_required(VERSION 3.20.0 FATAL_ERROR)
 project(unified-runtime VERSION 0.9.0)
 
 include(GNUInstallDirs)

README.md

@@ -87,7 +87,7 @@ for more detailed instructions on the correct setup.
 
 Required packages:
 - C++ compiler with C++17 support
-- [CMake](https://cmake.org/) >= 3.14.0
+- [CMake](https://cmake.org/) >= 3.20.0
 - Python v3.6.6 or later
 
 ### Windows