netsend version 0.0~svnr250-1.1 failed to build on amd64 with GCC-4.6/oneiric

netsend version 0.0~svnr250-1.1 failed to build on amd64 with GCC-4.6/oneiric
Link to failed build: https://launchpad.net/ubuntu/+archive/test-rebuild-20110413/+buildjob/2463155

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/2463155/+files/buildlog_ubuntu-natty-amd64.netsend_0.0%7Esvnr250-1.1_FAILEDTOBUILD.txt.gz

This log snippet might be of interest, since it triggered the matcher 'Purging chroot-autobuild'.
Excerpt 344 lines into the build log:

cc -Wall -W -Wwrite-strings -Wsign-compare -Wpointer-arith -Wcast-qual -Wcast-align -Wstrict-prototypes -Wmissing-prototypes -Wnested-externs -Winline -Wshadow -Wformat=2 -Wall -g -O2 --param max-inline-insns-single=400 -c proto_tcp_trans.c -o proto_tcp_trans.o
cc -Wall -W -Wwrite-strings -Wsign-compare -Wpointer-arith -Wcast-qual -Wcast-align -Wstrict-prototypes -Wmissing-prototypes -Wnested-externs -Winline -Wshadow -Wformat=2 -Wall -g -O2 --param max-inline-insns-single=400 -c proto_udp_trans.c -o proto_udp_trans.o
cc -Wall -W -Wwrite-strings -Wsign-compare -Wpointer-arith -Wcast-qual -Wcast-align -Wstrict-prototypes -Wmissing-prototypes -Wnested-externs -Winline -Wshadow -Wformat=2 -Wall -g -O2 --param max-inline-insns-single=400 -c proto_udplite_trans.c -o proto_udplite_trans.o
cc -Wall -W -Wwrite-strings -Wsign-compare -Wpointer-arith -Wcast-qual -Wcast-align -Wstrict-prototypes -Wmissing-prototypes -Wnested-externs -Winline -Wshadow -Wformat=2 -Wall -g -O2 --param max-inline-insns-single=400 -c proto_udplite_recv.c -o proto_udplite_recv.o
cc -Wall -W -Wwrite-strings -Wsign-compare -Wpointer-arith -Wcast-qual -Wcast-align -Wstrict-prototypes -Wmissing-prototypes -Wnested-externs -Winline -Wshadow -Wformat=2 -Wall -g -O2 --param max-inline-insns-single=400 -c proto_dccp_trans.c -o proto_dccp_trans.o
cc -Wall -W -Wwrite-strings -Wsign-compare -Wpointer-arith -Wcast-qual -Wcast-align -Wstrict-prototypes -Wmissing-prototypes -Wnested-externs -Winline -Wshadow -Wformat=2 -Wall -g -O2 --param max-inline-insns-single=400 -c proto_sctp_trans.c -o proto_sctp_trans.o
cc -Wall -W -Wwrite-strings -Wsign-compare -Wpointer-arith -Wcast-qual -Wcast-align -Wstrict-prototypes -Wmissing-prototypes -Wnested-externs -Winline -Wshadow -Wformat=2 -Wall -g -O2 --param max-inline-insns-single=400 -c proto_tipc_trans.c -o proto_tipc_trans.o
cc -lm -Wall -W -Wwrite-strings -Wsign-compare -Wpointer-arith -Wcast-qual -Wcast-align -Wstrict-prototypes -Wmissing-prototypes -Wnested-externs -Winline -Wshadow -Wformat=2 -Wall -g -O2 --param max-inline-insns-single=400 -o netsend analyze.o error.o file.o getopt.o main.o net.o proto_tipc.o proto_udp_recv.o receive.o trans_common.o ns_hdr.o xfuncs.o proto_tcp_trans.o proto_udp_trans.o proto_udplite_trans.o proto_udplite_recv.o proto_dccp_trans.o proto_sctp_trans.o proto_tipc_trans.o
ns_hdr.o: In function `probe_rtt':
/build/buildd/netsend-0.0~svnr250/ns_hdr.c:204: undefined reference to `sqrt'
collect2: ld returned 1 exit status
make[1]: *** [netsend] Error 1
make[1]: Leaving directory `/build/buildd/netsend-0.0~svnr250'
make: *** [build-stamp] Error 2
dpkg-buildpackage: error: debian/rules build gave error exit status 2
******************************************************************************
Build finished at 20110425-0019
FAILED [dpkg-buildpackage died]
Purging chroot-autobuild/build/buildd/netsend-0.0~svnr250