configure + make fails on AIX due to missing -lpthread

After the following:
 ./configure --prefix=/opt --sysconfdir=/var/rcs/etc
--sharedstatedir=/var/rcs/com --localstatedir=/var/rcs
--mandir=/usr/share/man --infodir=/opt/share/info/rcs

make proceeds normally until the programs need to 'link' - ident is the
first failure:

To succeed, copy/paste then add -lpthread and the command succeeds

======
root@x064:[/data/prj/gnu/rcs/rcs-5.9.4]make
Making all in lib
make[1]: Entering directory `/data/prj/gnu/rcs/rcs-5.9.4/lib'
make  all-recursive
make[2]: Entering directory `/data/prj/gnu/rcs/rcs-5.9.4/lib'
make[3]: Entering directory `/data/prj/gnu/rcs/rcs-5.9.4/lib'
make[3]: Nothing to be done for `all-am'.
make[3]: Leaving directory `/data/prj/gnu/rcs/rcs-5.9.4/lib'
make[2]: Leaving directory `/data/prj/gnu/rcs/rcs-5.9.4/lib'
make[1]: Leaving directory `/data/prj/gnu/rcs/rcs-5.9.4/lib'
Making all in doc
make[1]: Entering directory `/data/prj/gnu/rcs/rcs-5.9.4/doc'
make[1]: Nothing to be done for `all'.
make[1]: Leaving directory `/data/prj/gnu/rcs/rcs-5.9.4/doc'
Making all in man
make[1]: Entering directory `/data/prj/gnu/rcs/rcs-5.9.4/man'
make  all-am
make[2]: Entering directory `/data/prj/gnu/rcs/rcs-5.9.4/man'
make[2]: Leaving directory `/data/prj/gnu/rcs/rcs-5.9.4/man'
make[1]: Leaving directory `/data/prj/gnu/rcs/rcs-5.9.4/man'
Making all in src
make[1]: Entering directory `/data/prj/gnu/rcs/rcs-5.9.4/src'
make  all-am
make[2]: Entering directory `/data/prj/gnu/rcs/rcs-5.9.4/src'
cc -qlanglvl=extc89 -qlanglvl=extc99 -qlanglvl=extc99  -g   -o ident
ident.o libparts.a -L../lib -lgnu
ld: 0711-317 ERROR: Undefined symbol: .pthread_setspecific
ld: 0711-317 ERROR: Undefined symbol: .pthread_getspecific
ld: 0711-317 ERROR: Undefined symbol: .pthread_once
ld: 0711-317 ERROR: Undefined symbol: .pthread_key_create
ld: 0711-345 Use the -bloadmap or -bnoquiet option to obtain more
information.
make[2]: *** [ident] Error 8
make[2]: Leaving directory `/data/prj/gnu/rcs/rcs-5.9.4/src'
make[1]: *** [all] Error 2
make[1]: Leaving directory `/data/prj/gnu/rcs/rcs-5.9.4/src'
make: *** [all-recursive] Error 1
root@x064:[/data/prj/gnu/rcs/rcs-5.9.4]cd src
root@x064:[/data/prj/gnu/rcs/rcs-5.9.4/src]cc -qlanglvl=extc89
-qlanglvl=extc99 -qlanglvl=extc99  -g   -o ident ident.o libparts.a
-L../lib -lgnu -lpthread

Just let me know what else you would like to receive.

Michael