target_overrides only allows to add extra features, not labels/macros/device_has

[AlessandroA]

The target_overrides config option only allows to add/remove custom features (FEATURE_*). Other symbols can only be overridden (the symbol needs to be there in the first place).

This means that it is not possible for target_overrides to add/remove a new label (TARGET_*), a new custom macro or a new DEVICE_HAS_* macro.

How to reproduce

If in an application you override the K64F target, this is allowed:

{
    "target_overrides": {
        "K64F": {
            "target.features_add": ["UVISOR"]
        }
    }
}

but this is not (compile error):

{
    "target_overrides": {
        "K64F": {
            "target.features_add": ["UVISOR"],
            "target.extra_labels_add": ["UVISOR_SUPPORTED"]
        }
    }
}

Additional notes

This feature was originally available for custom targets (which BTW are not working any more, see #2196 and this related issue).

In the case of the uVisor hello-world example and other similar applications, though, it is not ideal to define custom targets. target_overrides are more natural.

This is a blocker for the release of the uVisor hello-world application.

@screamerbg @meriac @mjs-arm

[sg-]

@geky please review

[geky]

I have a branch that should properly handle cumulative overrides now:
master...geky:tools-cumulative-overrides

@screamerbg, @theotherjimmy, does this seem reasonable?

I don't know if it is correctly handling the uVisor supported label though, there are several special cases in the build tools (example).

[geky]

Moved to pr: #2215

[ciarmcom]

ARM Internal Ref: IOTMORF-124

[sg-]

@AlessandroA is this resolved?

[AlessandroA]

@sg- Yes, it was fixed by the linked PR. Closing the issue.