Increase required CMake version to 3.9

[andrewhop]

Description of changes:

CMake 4.0 is coming out soon and requires cmake_minimum_required to be at least 3.5:

Compatibility with versions of CMake older than 3.5 has been removed. Calls to cmake_minimum_required() or cmake_policy() that set the policy version to an older value now issue an error

The common runtime and s2n-tls upgraded to 3.9 last year.

Call-outs:

This will break any customer using CMake version less than 3.9 which was released in November 2018

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license and the ISC license.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.05%. Comparing base (4898adb) to head (51b1e01).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2219      +/-   ##
==========================================
- Coverage   79.06%   79.05%   -0.01%     
==========================================
  Files         612      612              
  Lines      106483   106511      +28     
  Branches    15050    15052       +2     
==========================================
+ Hits        84192    84206      +14     
- Misses      21639    21652      +13     
- Partials      652      653       +1     

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[darylmartin100]

The common runtime still supports older CMAKE versions via cmake_minimum_required(VERSION 3.9...3.31). If we merge this we break customers on older versions of CMAKE no?

[andrewhop]

We're using the same minimum version: 3.9. cmake_minimum_required(VERSION 3.9...3.31) is setting the minimum to 3.9 and the maximum to 3.31. I thought about adding that but figured that might cause issues if we forget to bump it in the future.

[LecrisUT]

It does not set a maximum version. What it does is that it sets policies defined between 3.9 and 3.31.

Please, please use the 3.9...3.31 or at the very least bump it to any version pinned to an lts distro that you support.