Build Fails with --enable-developer when building without libtool

Build Fails with --enable-developer when building master without libtool (same results whether it was not detected, or --without-libtool was explicitly specified). This was found across all systems in Jenkins.

example of build failure (trimmed):

gcc   -I/home/jenkins/workspace/bind9-multiconfig-master/34e98e4d -I../../.. -I/home/jenkins/workspace/bind9-multiconfig-master/34e98e4d/lib/dns/include -I../../../lib/dns/include -I/home/jenkins/workspace/bind9-multiconfig-master/34e98e4d/lib/isc/include -I../../../lib/isc -I../../../lib/isc/include -I../../../lib/isc/unix/include -I../../../lib/isc/pthreads/include -I../../../lib/isc/x86_32/include -I/home/jenkins/workspace/bind9-multiconfig-master/34e98e4d/lib/isccfg/include -I../../../lib/isccfg/include -I/usr/include  -I/home/jenkins/opt/atf/include   -DISC_MEM_DEFAULTFILL=1 -DISC_LIST_CHECKINIT=1 -DNS_HOOKS_ENABLE=1 -D_GNU_SOURCE -DNS_HOOKS_ENABLE=1 -g  -W -Wall -Wmissing-prototypes -Wcast-qual -Wwrite-strings -Wformat -Wpointer-arith -fno-strict-aliasing -fno-delete-null-pointer-checks -Wshadow -Werror  -L/home/jenkins/opt/fstrm/lib -o backtrace_test_nosymtbl \
./backtrace_test.c ../../../lib/isc/libisc.a -L/usr/lib -lcrypto -ldl -lprotobuf-c -lfstrm -ldl -lz -ljson-c -llmdb   -lxml2 
../../../lib/isc/libisc.a(result.o): In function `initialize':
/home/jenkins/workspace/bind9-multiconfig-master/34e98e4d/lib/isc/result.c:247: undefined reference to `pthread_once'
../../../lib/isc/libisc.a(mutex.o): In function `initialize_attr':
/home/jenkins/workspace/bind9-multiconfig-master/34e98e4d/lib/isc/pthreads/mutex.c:270: undefined reference to `pthread_mutexattr_init'