Generate *.cbuild-mlops.yml even a project component is missing

[ReinhardKeil]

Describe The Problem To Be Solved

Executorch workflow generates a *.clayer.yml with components. But the starting point is that this file is missing.
This workflow needs the *.cbuild-mlops.yml as input

cbuild setup does not generate *.cbuild-mlops.yml when a *.clayer.yml is missing.
Make the generation of *.cbuild-mlops.yml even when project components are missing.

Test Project https://github.com/Arm-Examples/CMSIS-Executorch - remove the ai_layer.clayer.yml for testing

[brondani]

Observation: contrary to this note in the reproducer, ai_layer.clayer.yml should be declared as an output even though run_export.py preserves its timestamp when the generated content is unchanged. CMake generates the corresponding Ninja edge with restat enabled, so a successful generation that leaves the file unchanged does not cause convert-model to run repeatedly.

[brondani]

@MatthiasHertelArm Please validate the changes #2580 with the next nightly build.