gnurobots version 2:1.2.0-4ubuntu2 failed to build on amd64 with GCC-4.6/oneiric

gnurobots version 2:1.2.0-4ubuntu2 failed to build on amd64 with GCC-4.6/oneiric
Link to failed build: https://launchpad.net/ubuntu/+archive/test-rebuild-20110413/+buildjob/2451718

Details about the rebuild:
https://lists.ubuntu.com/archives/ubuntu-devel/2011-April/033042.html

Direct link to the build log: https://launchpad.net/ubuntu/+archive/test-rebuild-20110413/+buildjob/2451718/+files/buildlog_ubuntu-natty-amd64.gnurobots_2%3A1.2.0-4ubuntu2_FAILEDTOBUILD.txt.gz

This log snippet might be of interest, since it triggered the matcher 'Purging chroot-autobuild'.
Excerpt 1984 lines into the build log:

/build/buildd/gnurobots-1.2.0/src/ui-arena.c:429: undefined reference to `g_usleep'
ui-arena.o: In function `ui_arena_robot_zap':
/build/buildd/gnurobots-1.2.0/src/ui-arena.c:438: undefined reference to `g_usleep'
ui-arena.o: In function `ui_arena_robot_feel':
/build/buildd/gnurobots-1.2.0/src/ui-arena.c:447: undefined reference to `g_usleep'
ui-arena.o:/build/buildd/gnurobots-1.2.0/src/ui-arena.c:456: more undefined references to `g_usleep' follow
collect2: ld returned 1 exit status
make[3]: *** [gnurobots] Error 1
make[3]: Leaving directory `/build/buildd/gnurobots-1.2.0/src'
make[2]: *** [all-recursive] Error 1
make[2]: Leaving directory `/build/buildd/gnurobots-1.2.0'
make[1]: *** [all] Error 2
make[1]: Leaving directory `/build/buildd/gnurobots-1.2.0'
make: *** [build-stamp] Error 2
dpkg-buildpackage: error: debian/rules build gave error exit status 2
******************************************************************************
Build finished at 20110423-0354
FAILED [dpkg-buildpackage died]
Purging chroot-autobuild/build/buildd/gnurobots-1.2.0