Fix inclusion of ffconfig.h

[josesimoes]

Description

• Add check to CMake for file existence.

Motivation and Context

• The "hard delete" approach that we are forced to use to get our ffconfig.h in IDF build causes issues when switching to a local build of a target that's not using SDCard after the build of another one that has SDCard. Like compiler error from recurring inclusion of header file. This new check for the file existence by CMake (and subsequence error) take care of this.

How Has This Been Tested?

Screenshots

Types of changes

• Improvement (non-breaking change that improves a feature, code or algorithm)
• Bug fix (non-breaking change which fixes an issue with code or algorithm)
• New feature (non-breaking change which adds functionality to code)
• Breaking change (fix or feature that would cause existing functionality to change)
• Config and build (change in the configuration and build system, has no impact on code or features)
• Dev Containers (changes related with Dev Containers, has no impact on code or features)
• Dependencies (update dependencies and changes associated, has no impact on code or features)
• Documentation (changes or updates in the documentation, has no impact on code or features)

Checklist

• My code follows the code style of this project (only if there are changes in source code).
• My changes require an update to the documentation (there are changes that require the docs website to be updated).
• I have updated the documentation accordingly (the changes require an update on the docs in this repo).
• I have read the CONTRIBUTING document.
• I have tested everything locally and all new and existing tests passed (only if there are changes in source code).

[nfbot]

Hey @josesimoes!

Seems that the build is failing for this PR... 😯 Please check it.