[arch-general] Howto setup i686 archroot on x86_64 box? (not linux32 chroot)

[David C. Rankin]

All,

  I have built all x86_64 packages in an archroot on my x86_64 box. I would like
to set up and i686 archroot on the same box to build the i686 packages on the
same box due to build times dropping from about 8 hours on i686 to less than 3
on the x86_64 box. I am unclear how best to do it -- or if it is doable.

  I've read https://wiki.archlinux.org/index.php/Arch64_FAQ about multilib with
~/.makepkg.i686.conf and a true linux32 chroot setup, but none of those are
specific to the archroot setup. Both seem like they would work, but don't know
if they are the right choice for build the 110 packages TDE requires. I would
like to do this in an archroot if possible.

  I use the "Classic Way" of handling the build specified in
https://wiki.archlinux.org/index.php/DeveloperWiki:Building_in_a_Clean_Chroot.
All dependency packages are installed in the rw layer of the chroot with the
first package built, a [local] repo is created under $CHROOT/root/repo, and as
packages are built, they are installed, the resulting package is copied to
$CHROOT/root/repo, and the repo index is updated with repo-add, and the process
repeats with the next package until the build of TDE is complete. (that chroot
is usually used to finish and tweaks needed for that set of package, then
deleted and a new archroot created for the next major set of updates)

  It seems like setting up another archroot, and installing multilib would allow
an archroot to work, but how would you tell makechrootpkg to build the i686
version instead of the x86_64 version. I don't want to have to modify the
PKGBUILDs or do a significant re-write of the build script that automates the
build, but if it is as simple as changing the makechrootpkg call, that would be
a simple config-file fix.

  How best to handle this? (or just use the old i686 box and run it overnight?)

-- 
David C. Rankin, J.D.,P.E.