configure script can't auto-detect aarch64

[MrHighVoltage]

As the title states, building cbc on aarch64 requires explicitly setting the build target architecture on aarch64.

It seems that the release-packages include config.guess and config.sub scripts from 2007, whereas in the repo, those files have been continuously updated.

Is it possible to re-release the current version with the newer files included? Or is there are reason for not updating those files?

Thank you very much!

[tkralphs]

Yes, there is a method to the madness. The stable/2.10 branch of Cbc and associated releases (as well as stable branches of dependencies and their releases) uses an older stable branch of our BuildTools that was developed back in the early '00s (https://github.com/coin-or-tools/BuildTools/tree/stable/0.8). Through an accumulation of homebrewed fixes that are only compatible with older version of the autotools, this version of the BuildTools became pegged to those older versions.

Over years, we eventually completely re-implemented the BuildTools in its master branch, so it is now up-to-date with current autotools. We have moved all of the master branches of the projects in the Cbc stack to this new version of the BuildTools, while at the same time undertaking some refactoring that was sorely needed. Unfortunately, that refactoring is still unfinished and would benefit from some volunteer effort, which has not materialized. I have a plan for getting it done as part of a research project, but that is a slow-moving train.

Because the move to the master branch of the BuildTools involves many breaking changes to existing build workflows, we cannot just retrofit the new build system onto the old stable versions. So everything is waiting for a new stable version of Cbc and associated releases.

If you are building your own binaries from source, the master branch is working fine and you can use it, there just may be some regressions that we need to track down and some parameter tuning is needed (as well as some additional refactoring).

[tkralphs]

In case you want to read about the refactoring, you can check the discussion here: #465.

[tkralphs]

Apparently, it works to do this.