Although dpkg-buildpackage has a -a $arch option, dpkg-checkbuilddeps does nothing with it. As a result, dpkg-checkbuilddeps may consider the build-dependencies satisfied when they actually aren't, because a package is installed for a wrong architecture. This is ok if you're already resolving dependencies with something like apt-get build-dep or mk-build-deps, but it does make it harder to test out fixes to the multiarch build-dependencies themselves.
ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: dpkg-dev 1.16.0.3ubuntu5
ProcVersionSignature: Ubuntu 3.1.0-3.3-generic 3.1.0
Uname: Linux 3.1.0-3-generic x86_64
ApportVersion: 1.23-0ubuntu4
Architecture: amd64
Date: Sat Nov 5 10:12:06 2011
InstallationMedia: Ubuntu 10.04.1 LTS "Lucid Lynx" - Release amd64 (20100816.1)
PackageArchitecture: all
ProcEnviron:
PATH=(custom, user)
LANG=en_US.UTF-8
SHELL=/bin/bash
SourcePackage: dpkg
UpgradeStatus: Upgraded to oneiric on 2011-09-23 (42 days ago)
Fixed in quantal and above as of dpkg version 1.16.3ubuntu1.