ci: output diff on code format failures

[glikely]

Description

It is useful to know why the format checks failed. When it happens, use git diff to display the change that is required.

Motivation and Context

This patch modifies check-cmake.sh to behave the same as check-format.sh. It now unconditionally reformats the file to meet convention which check-changes.sh can detect. Then check-changes.sh can display all the formatting changes in the build log, making it easier to fix the issues quickly.

How Has This Been Tested?

Tested locally and via GitHub actions CI

Example of output when formatting changes are needed can be seen here: https://github.com/glikely/obs-plugintemplate/actions/runs/4366259875/jobs/7636020253#step:7:1

Types of changes

• New feature (non-breaking change which adds functionality)

Checklist:

• [x] My code has been run through clang-format.
• [x] I have read the contributing document.
• [x] My code is not on the master branch.
• [x] The code has been tested.
• [x] All commit messages are properly formatted and commits squashed where appropriate.
• [x] I have included updates to all appropriate documentation.