#1 can't find libXext

[hobgoblin]

I am a newbie so please forgive my ignorance if I am
missing something very obvious but...

I get the following error when running configure:

...checking for snprintf... yes
checking for X... libraries /usr/X11R6/lib, headers
/usr/X11R6/include
checking for IceConnectionNumber in -lICE... (cached) no
checking for libXext... no
configure: error: We need a working libXext to proceed.
Since configure can't find it itself, we stop here
assuming that make wouldn't find them either.

I have the required libraries here:

hispaniola:/usr/share/reader # locate libXext
/usr/X11R6/lib/libXext.so.6
/usr/X11R6/lib/libXext.so.6.4
/usr/X11R6/lib64/libXext.so.6
/usr/X11R6/lib64/libXext.so.6.4

But how do I get configure (and make) to recognise
their location. There are no obvious configure options
or environment variables that would point it in the
right direction.

Otherwise, sounds like a great program, can't wait to
get it working.

Thankyou