[build2] Kconfig support in build2

[Matthew Krupcale]

On Tue, Jan 19, 2021 at 7:04 AM Boris Kolpackov via users
<users at build2.org> wrote:
>
> The build2 toolchain now includes a build system module that allows using
> the Linux kernel configuration system (Kconfig) to configure build2-based
> projects.

Pretty cool. Linux Kconfig is both proven and powerful, and this shows
the versatility of build2 modules.

Is libbuild2-kconfig only on GitHub right now, or is it available on
git.build2.org somewhere? Not a big deal either way--I just need to
know where the best place to get release tarballs is. I see it's
currently in https://stage.build2.org/1/build2, but presumably it will
appear in https://pkg.cppget.org/1/alpha/build2/ at release like the
rest of build2?

Also, I am planning on packaging libbuild2-kconfig as a separate
Fedora package from the main build2 package (which currently also
provides libbuild2, libbutl, [lib]bpkg, and bdep subpackages), since
it will keep the main package from becoming too unwieldy. However,
updating build2 to e.g. v0.15.0 without also rebuilding
libbuild2-kconfig would leave e.g. libbuild2-kconfig-0.14.0-0.1.so
which cannot be loaded by the new build2 driver[1,2]. This can be
handled in the Fedora build system using so-called side tags[3]. That
is, so as long as both packages are submitted for the updates
repository together under a side tag, everything should continue to
work.

At some point it might also make sense to move some of the build2
subpackages to their own package to reduce the amount of rebuilding
required (i.e. if their release schedules ever begin to diverge from
the main build2 package).

Best,
Matthew

[1] https://lists.build2.org/archives/users/2019-October/000687.html
[2] https://lists.build2.org/archives/users/2019-October/000693.html
[3] https://fedoraproject.org/wiki/User:Nphilipp/Package_update_HOWTO#Multiple_Packages