pam fails to cross-build

pam fail to cross-build with:

arm-linux-gnueabi-gcc -DHAVE_CONFIG_H -I. -I../.. -g -O2 -W -Wall -Wbad-function-cast -Wcast-align -Wcast-qual -Wmissing-declarations -Wmissing-prototypes -Wpointer-arith -Wreturn-type -Wstrict-prototypes -Wwrite-strings -Winline -Wshadow -c pam_conv_y.c
/bin/bash ../../libtool --tag=CC --mode=link arm-linux-gnueabi-gcc -g -O2 -W -Wall -Wbad-function-cast -Wcast-align -Wcast-qual -Wmissing-declarations -Wmissing-prototypes -Wpointer-arith -Wreturn-type -Wstrict-prototypes -Wwrite-strings -Winline -Wshadow -Wl,-z,defs -Wl,--as-needed -Wl,-O1 -o pam_conv1 pam_conv_l.o pam_conv_y.o
libtool: link: arm-linux-gnueabi-gcc -g -O2 -W -Wall -Wbad-function-cast -Wcast-align -Wcast-qual -Wmissing-declarations -Wmissing-prototypes -Wpointer-arith -Wreturn-type -Wstrict-prototypes -Wwrite-strings -Winline -Wshadow -Wl,-z -Wl,defs -Wl,--as-needed -Wl,-O1 -o pam_conv1 pam_conv_l.o pam_conv_y.o
pam_conv_l.o: In function `yylex':
/home/wookey/testing/build/build/xdeb/pam/conf/pam_conv1/pam_conv_l.c:871: undefined reference to `yywrap'

This is a problem with flex processing.

Background:
The build command is:
xdeb --only-explicit -a armel --prefer-apt --apt-source --debug --force-rebuild pam

The actual build command xdeb issues is:
debuild --no-lintian -eUSER -eCONFIG_SITE=/etc/dpkg-cross/cross-config.armel -eDEB_BUILD_OPTIONS=nocheck -eGTEST_INCLUDEDIR=/usr/arm-linux-gnueabi/include -eGTEST_LIBDIR=/usr/arm-linux-gnueabi/lib -ePKG_CONFIG_LIBDIR=/usr/arm-linux-gnueabi/lib/pkgconfig:/usr/arm-linux-gnueabi/share/pkgconfig:/usr/share/pkgconfig -eDH_VERBOSE=1 -aarmel -b -uc -us -tc

To easily reproduce the build environment in which this bug was discovered follow the HOWTO here:
https://wiki.linaro.org/Platform/DevPlatform/CrossCompile/CrossBuildNano