CMake: 3.18.2 minimum version set

0xc0170 · 0xc0170 · commit 6ae34a6b65bf · 2020-09-04T08:25:50.000+01:00
There are fixes in the latest version we need for ARMClang.
diff --git a/CMakeLists.txt b/CMakeLists.txt
@@ -3,7 +3,7 @@
 
 # This is the boilerplate for Mbed OS
 
-cmake_minimum_required(VERSION 3.13 FATAL_ERROR)
+cmake_minimum_required(VERSION 3.18.2 FATAL_ERROR)
 
 # Using relative paths behavior
 if(POLICY CMP0076)
