perl fails to cross-build

[Wookey]

perl fails to cross-build with a lot of undefined references to pthread*

cc -fstack-protector -L/usr/local/lib -o miniperl \
       gv.o toke.o perly.o pad.o regcomp.o dump.o util.o mg.o reentr.o mro.o hv.o av.o run.o pp_hot.o sv.o pp.o scope.o pp_ctl.o pp_sys.o doop.o doio.o regexec.o utf8.o taint.o deb.o universal.o xsutils.o globals.o perlio.o perlapi.o numeric.o mathoms.o locale.o pp_pack.o pp_sort.o \
     miniperlmain.o opmini.o perlmini.o
util.o: In function `Perl_safesysmalloc':
/home/wookey/testing/build/build/xdeb/perl/util.c:78: undefined reference to `pthread_getspecific'
util.o: In function `Perl_safesysrealloc':
/home/wookey/testing/build/build/xdeb/perl/util.c:134: undefined reference to `pthread_getspecific'
util.o: In function `Perl_croak_nocontext':
/home/wookey/testing/build/build/xdeb/perl/util.c:1444: undefined reference to `pthread_getspecific'
util.o: In function `Perl_safesyscalloc':
/home/wookey/testing/build/build/xdeb/perl/util.c:271: undefined reference to `pthread_getspecific'
util.o: In function `Perl_die_nocontext':
/home/wookey/testing/build/build/xdeb/perl/util.c:1397: undefined reference to `pthread_getspecific'

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

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

[Wookey (wookey)]

With a large cross building patch applied it gets much further, and instead dies trying to link wrong-arch libbz2:

arm-linux-gnueabi-gcc -shared -O2 -g -fstack-protector Bzip2.o -o /home/wookey/testing/build/build/xdeb/perl-5.10.1/lib/arm-linux-gnueabi/auto/Compress/Raw/Bzip2/Bzip2.so \
    -L/usr/lib -lbz2 \

/usr/lib/libbz2.so: file not recognized: File format not recognized

Patched version of perl is in https://launchpad.net/~linaro-foundations/+archive/cross-alip

Build-log attached.

[Wookey (wookey)]

Some info on the perl cross patches is provided here: https://wiki.linaro.org/Platform/DevPlatform/CrossCompile/CrossBuildingPerl