[Buildroot] Package can create LINUX_FINAL_RECURSIVE_DEPENDENCIES

[Yann E. MORIN <yann.morin.1998@free.fr>]

Heiko, All,

On 2020-01-24 08:37 +0100, Heiko Thiery spake thusly:
> I have a custom package (MYPACKAGE) in my BR2_EXTERNAL. This package
> uses the "$(eval $(kernel-module))". In addition this package also
> adds a kernel patch hook via BR2_EXTERNAL/linux-ext-MYPACKAGE.mk.
> 
> As far as I see MYPACKAGE depends on linux (due to kernel-module) and
> LINUX depends on MYPACKAGE due to the dependency created to
> LINUX_PATCH_DEPENDENCIES.

While reviewing our existing linux extensions to prepare my previous
reply, I noticed that we do have the same problem in Buildroot itself.
The package that provides the RTAI extension has an explicit dependency
on linux:

    https://git.buildroot.org/buildroot/tree/package/rtai/rtai.mk#n19

And indeed, runing 'make legal-info' does break in a similar fashion:

    package/rtai/rtai.mk:32: *** Recursive variable
    'RTAI_FINAL_RECURSIVE_DEPENDENCIES' references itself (eventually).
    Stop.

Damned... :-/ We'll have to come up with a fix...

Regards,
Yann E. MORIN.

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