TODO: Revert this to use obsproject/obs-studio for release tagged after 31.0.0.

Important :

• This PR Should be reverted to new obs-plugintemplate when the fix (macos SDK detection) is available in a tagged release.
• This PR is "ahead" of the obs-plugin-template & obs-studio 31.0.3 tag.
• This PR relies only on a fork of the 31.0.0 code-base from obs-studio OBS Project.

This fix solves:

• Mac OS SDK detection in the OBS source both for local build & github action.

What has been done :

• Forked obs-studio master on DistroAV repo: https://github.com/DistroAV/obs-studio
• Re-created a 31.0.0 tag at the same commit
• Added changed (committed to upstream) from :
  cmake: Adjust macOS SDK detection obsproject/obs-studio#11893

Also similar to :
obsproject/obs-studio#12076

• Added a 31.0.0-fix tag containing this unique change
• Update BuildSpecs to use the fixed version of the OBS source instead of the upstream.

IMPORTANT

This is an exceptional & temporary change to allow the project to create new releases.

This MUST be reverted to the proper Obs upstream buildspec as soon as the obs-plugin-template implement the required changes.