mach version 0.9.1-3 failed to build in oneiric

mach version 0.9.1-3 failed to build in oneiric
Link to failed build: https://launchpad.net/ubuntu/+archive/test-rebuild-20110816/+build/2704576

Details about the rebuild:
http://people.ubuntuwire.org/~wgrant/rebuild-ftbfs-test/test-rebuild-20110816-oneiric.html

Direct link to the build log: https://launchpad.net/ubuntu/+archive/test-rebuild-20110816/+build/2704576/+files/buildlog_ubuntu-oneiric-amd64.mach_0.9.1-3_FAILEDTOBUILD.txt.gz

This log snippet might be of interest, since it triggered the matcher 'Purging chroot-autobuild'.
Excerpt 664 lines into the build log:

creating libselinux-mach.la
(cd .libs && rm -f libselinux-mach.la && ln -s ../libselinux-mach.la libselinux-mach.la)
gcc -DHAVE_CONFIG_H -I. -I. -I.. -Wall -Werror -g -O2 -g -O2 -Wall -c mach-helper.c
mach-helper.c: In function 'do_command':
mach-helper.c:147:7: error: variable 'retval' set but not used [-Werror=unused-but-set-variable]
cc1: all warnings being treated as errors

make[3]: *** [mach-helper.o] Error 1
make[3]: Leaving directory `/build/buildd/mach-0.9.1/src'
make[2]: *** [all-recursive] Error 1
make[2]: Leaving directory `/build/buildd/mach-0.9.1'
make[1]: *** [all] Error 2
make[1]: Leaving directory `/build/buildd/mach-0.9.1'
make: *** [debian/stamp-makefile-build] Error 2
dpkg-buildpackage: error: debian/rules build gave error exit status 2
******************************************************************************
Build finished at 20110822-0715
FAILED [dpkg-buildpackage died]
Purging chroot-autobuild/build/buildd/mach-0.9.1