plasma-widget-kbstate version 2.0~svn906377-0ubuntu7 failed to build in oneiric

plasma-widget-kbstate version 2.0~svn906377-0ubuntu7 failed to build in oneiric
Link to failed build: https://launchpad.net/ubuntu/+archive/test-rebuild-20110816/+build/2708293

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/2708293/+files/buildlog_ubuntu-oneiric-amd64.plasma-widget-kbstate_2.0%7Esvn906377-0ubuntu7_FAILEDTOBUILD.txt.gz

This log snippet might be of interest, since it triggered the matcher 'Purging chroot-autobuild'.
Excerpt 985 lines into the build log:

-- Performing Test __KDE_HAVE_GCC_VISIBILITY - Success
-- Found KDE 4.7 include dir: /usr/include
-- Found KDE 4.7 library dir: /usr/lib
-- Found the KDE4 kconfig_compiler preprocessor: /usr/bin/kconfig_compiler
-- Found automoc4: /usr/bin/automoc4
CMake Error at /usr/share/kde4/apps/cmake/modules/FindX11.cmake:390 (MESSAGE):
  Could not find X11
Call Stack (most recent call first):
  CMakeLists.txt:7 (find_package)

-- Configuring incomplete, errors occurred!
dh_auto_configure: cmake .. -DCMAKE_INSTALL_PREFIX=/usr -DCMAKE_VERBOSE_MAKEFILE=ON -DCMAKE_BUILD_TYPE=Debian returned exit code 1
make: *** [build] Error 2
dpkg-buildpackage: error: debian/rules build gave error exit status 2
******************************************************************************
Build finished at 20110823-0303
FAILED [dpkg-buildpackage died]
Purging chroot-autobuild/build/buildd/plasma-widget-kbstate-2.0~svn906377