netperf: FTBFS with GCC 5: undefined reference to `demo_interval_tick'

Imported from Debian bug http://bugs.debian.org/798789:

Package: netperf
Version: 2.6.0-2
Severity: serious
Tags: sid stretch
Justification: fails to build from source (but built successfully in the past)

Hi,

netperf FTBFS in sid with GCC5:

[...]
gcc -DHAVE_CONFIG_H -I. -I.. -D_FORTIFY_SOURCE=2 -g -O2 -fstack-protector-strong -Wformat -Werror=format-security -Wall -c netlib.c
netlib.c: In function 'bind_to_specific_processor':
netlib.c:2292:9: warning: implicit declaration of function 'sched_setaffinity' [-Wimplicit-function-declaration]
     if (sched_setaffinity(getpid(), len, &netperf_cpu_set)) {
         ^
netlib.c: At top level:
netlib.c:4080:20: warning: 'temp_demo_ptr' is static but used in inline function 'demo_interval_tick' which is not static
     demo_two_ptr = temp_demo_ptr;
                    ^
netlib.c:4080:5: warning: 'demo_two_ptr' is static but used in inline function 'demo_interval_tick' which is not static
     demo_two_ptr = temp_demo_ptr;
     ^
netlib.c:4079:20: warning: 'demo_two_ptr' is static but used in inline function 'demo_interval_tick' which is not static
     demo_one_ptr = demo_two_ptr;
                    ^
[...]
gcc -g -O2 -fstack-protector-strong -Wformat -Werror=format-security -Wall -Wl,-z,relro -o netperf netperf.o netlib.o netsh.o nettest_bsd.o nettest_dlpi.o nettest_unix.o nettest_xti.o nettest_sctp.o nettest_sdp.o nettest_omni.o net_uuid.o dscp.o netcpu_procstat.o netrt_rtnetlink.o netdrv_ethtool.o netslot_linux.o netsys_linux.o netsec_linux.o -ldl -lm
nettest_omni.o: In function `send_omni_inner':
/tmp/buildd/netperf-2.6.0/src/nettest_omni.c:4366: undefined reference to `demo_interval_tick'
/tmp/buildd/netperf-2.6.0/src/nettest_omni.c:4359: undefined reference to `demo_interval_tick'
/tmp/buildd/netperf-2.6.0/src/nettest_omni.c:4363: undefined reference to `demo_interval_tick'
/tmp/buildd/netperf-2.6.0/src/nettest_omni.c:4356: undefined reference to `demo_interval_tick'
collect2: error: ld returned 1 exit status
[...]

Andreas