Fix CHANGELOG if not exist

[cyr-ius]

CPACK - Variable CHANGELOG if not exist

Description

When build old version , changelog is empty , because git list since last month.

Motivation and Context

Fix this.

How Has This Been Tested?

CPack old version Krypton 17.0 is OK

Screenshots (if appropriate):

Types of change

• [X ] 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:

• [X ] My code follows the Code guidelines of this project
• My change requires a change to the documentation, either Doxygen or wiki
• I have updated the documentation accordingly
• I have read the CONTRIBUTING document
• [] I have added tests to cover my change
• All new and existing tests passed

[wsnipex]

could you fix the git log --since so that it always returns something instead?
--since="30 days ago" should work

[cyr-ius]

OK , i changed. It works.