[DEV] Support multiple targets

[Louson]

Enable the build of several targets in the same build directory. The field 'target' in the menu can be a single string or an array of string. If given an array, all entries will be built (the build order is undefined).

This does not affect the previous 'target' behaviour.

[Louson]

Linked to issue #103

[Louson]

An undefined behavior remains concerning the inheritance:

Inherit from a virtual build configuration an set a bitbake target

This removes the virtual bitbake target

Inherit from a normal build configuration and set a bitbake target

This removes previous targets, but maybe we want to merge them ?

Inherit from multiple virtual build configurations

Should we merge all bitbake targets ?

Inherit from multiple build configurations with at least one non virtual

Should we merge all non virtual bitbake targets ?

[pboettch]

An undefined behavior remains concerning the inheritance:

Inherit from a virtual build configuration an set a bitbake target

This removes the virtual bitbake target

Inherit from a normal build configuration and set a bitbake target

This removes previous targets, but maybe we want to merge them ?

Inherit from multiple virtual build configurations

Should we merge all bitbake targets ?

Inherit from multiple build configurations with at least one non virtual

Should we merge all non virtual bitbake targets ?

I think targets should be overridden by the final build. As you have done your implementation.

Parent build-targets have most like no sens in this inherited build-configuration. At least not for image-targets.

What is actually your use-case? What are the multiple targets you are building within one build-config/build-dir using the same local.conf and thus machine.conf etc. I only can think of non-image-targets. Please enlighten us.

[Louson]

Well, there is nothing I want to do with inheritance. I was just wondering.

In my case I am creating training courses. I will use the beaglebone for all projects. I'd like to build them all together.

[pboettch]

After discussing with @cpb- we understood that currently the target-field is overwritten if a parent has it. Your patch does the same with list of targets. So it's fine, let's discuss this in another thread or issue if this needs a change.

[pboettch]

Regarding your multiple targets. You are build several images with the same machine.conf? Is that what you're saiing?

[Louson]

Yes, same machine.conf, same local.conf, same layers

[pboettch]

Just with different package selections, or something different?

[Louson]

Mainly. More generally, I would say whatever can be defined in your .bb