x11/gtk2 "Checks for JPEG loader failed"

Hi, trying to build gtk2 on solaris 10, using sunstudio 10. I've got everything
built and installed (including jpg) but gtk2 dies during the configure phase
with the following error:

checking for jpeglib.h... no
configure: WARNING: *** JPEG loader will not be built (JPEG header file not
found) ***
configure: error:
*** Checks for JPEG loader failed. You can build without it by passing
*** --without-libjpeg to configure but some programs using GTK+ may
*** not work properly
*** Error code 1

Stop.
bmake: stopped in /usr/pkgsrc/x11/gtk2
*** Error code 1

I've tried playing with CFLAGS, CPPFLAGS and even edited options.mk (to include
--without-libjpeg) and I've gone so far as to pkg_delete tiff and jpeg and
rebuild them; but I still get the same error. 

Can anyone tell me what they think is going wrong and how I can get around this?