Include ssl.h for cmock/ceedling

[kp-thomas-yau]

Description

Ceedling/CMock cannot find ssl.h when we run ceedling test on a dev machine

Test 'test_conn.c'
------------------
Generating include list for fake_dispatch.h...
Generating include list for frag.h...
Generating include list for wolf.h...
Generating include list for pmtud.h...
ERROR: Found no file 'ssl.h' in search paths.
rake aborted!

Includes the ssl file for UNIX system from now on

Motivation and Context

How Has This Been Tested?

Ran ceedling tests locally with the error gone

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• All active GitHub checks are passing
• The correct base branch is being used, if not main