cifer version 1.2.0-0ubuntu1 failed to build on i386

cifer version 1.2.0-0ubuntu1 failed to build on i386
Link to failed build: https://launchpad.net/ubuntu/+archive/test-rebuild-20110413/+buildjob/2447298

Direct link to the build log: https://launchpad.net/ubuntu/+archive/test-rebuild-20110413/+buildjob/2447298/+files/buildlog_ubuntu-natty-i386.cifer_1.2.0-0ubuntu1_FAILEDTOBUILD.txt.gz

This log snippet might be of interest, since it triggered the matcher 'Purging chroot-autobuild'.
Excerpt 859 lines into the build log:

gcc -DVERSION="\"1.2.0\"" -c -O2 src/polybius.c -o src/polybius.o
gcc -DVERSION="\"1.2.0\"" -c -O2 src/rf.c -o src/rf.o
gcc -DVERSION="\"1.2.0\"" -c -O2 src/shell.c -o src/shell.o
gcc -DVERSION="\"1.2.0\"" -c -O2 src/utility.c -o src/utility.o
gcc -DVERSION="\"1.2.0\"" -c -O2 src/vigenere.c -o src/vigenere.o
gcc -O2 -lreadline -o cifer src/actions_analysis.o src/actions_ciphers.o src/actions_head.o src/actions_io.o src/actions_shell.o src/actions_utility.o src/affine.o src/bacon.o src/ciphers.o src/columnar_transposition.o src/command.o src/dictionary.o src/frequency_analysis.o src/frequency_data.o src/interface.o src/io.o src/keyword.o src/main.o src/polybius.o src/rf.o src/shell.o src/utility.o src/vigenere.o
src/shell.o: In function `rl_gets':
shell.c:(.text+0x26): undefined reference to `readline'
src/shell.o: In function `cfsh_read':
shell.c:(.text+0x7a5): undefined reference to `add_history'
collect2: ld returned 1 exit status
make[1]: *** [cifer] Error 1
make[1]: Leaving directory `/build/buildd/cifer-1.2.0'
make: *** [build-stamp] Error 2
dpkg-buildpackage: error: debian/rules build gave error exit status 2
******************************************************************************
Build finished at 20110419-1248
FAILED [dpkg-buildpackage died]
Purging chroot-autobuild/build/buildd/cifer-1.2.0