dovecot-metadata-plugin version 0.0.1~hg144-0ubuntu1 failed to build in oneiric

dovecot-metadata-plugin version 0.0.1~hg144-0ubuntu1 failed to build in oneiric
Link to failed build: https://launchpad.net/ubuntu/+archive/test-rebuild-20110816/+build/2691754

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/2691754/+files/buildlog_ubuntu-oneiric-amd64.dovecot-metadata-plugin_0.0.1%7Ehg144-0ubuntu1_FAILEDTOBUILD.txt.gz

This log snippet might be of interest, since it triggered the matcher 'Purging chroot-autobuild'.
Excerpt 410 lines into the build log:

Making all in src
make[3]: Entering directory `/build/buildd/dovecot-metadata-plugin-0.0.1~hg144/src'
/bin/bash ../libtool --tag=CC --mode=compile gcc -DHAVE_CONFIG_H -I. -I.. -I -I/src/lib -I/src/lib-mail -I/src/lib-imap -I/src/lib-storage -I/src/lib-dict -I/src/imap -DPKG_RUNDIR=\"""\" -g -O2 -c -o metadata-plugin.lo metadata-plugin.c
libtool: compile: gcc -DHAVE_CONFIG_H -I. -I.. -I -I/src/lib -I/src/lib-mail -I/src/lib-imap -I/src/lib-storage -I/src/lib-dict -I/src/imap -DPKG_RUNDIR=\"\" -g -O2 -c metadata-plugin.c -fPIC -DPIC -o .libs/metadata-plugin.o
metadata-plugin.c:9:17: fatal error: lib.h: No such file or directory
compilation terminated.
make[3]: *** [metadata-plugin.lo] Error 1
make[3]: Leaving directory `/build/buildd/dovecot-metadata-plugin-0.0.1~hg144/src'
make[2]: *** [all-recursive] Error 1
make[2]: Leaving directory `/build/buildd/dovecot-metadata-plugin-0.0.1~hg144'
make[1]: *** [all] Error 2
make[1]: Leaving directory `/build/buildd/dovecot-metadata-plugin-0.0.1~hg144'
dh_auto_build: make -j1 returned exit code 2
make: *** [build] Error 2
dpkg-buildpackage: error: debian/rules build gave error exit status 2
******************************************************************************
Build finished at 20110820-0720
FAILED [dpkg-buildpackage died]
Purging chroot-autobuild/build/buildd/dovecot-metadata-plugin-0.0.1~hg144