checking readline/history.h usability... yes
  checking readline/history.h presence... yes
  checking for readline/history.h... yes
  checking for add_history in -lhistory... no
  configure: error: *** Can't find History headers and libs
  *** Error code 1

Basically you have to look at config.log to see the 'failed program'
that it tried to compile.  Sometimes configure scripts manually look
for headers, or do other odd things.

Note that NetBSD has some sort of readline emulation for editline.

I didn't see a line requiring readline in your build log.

You may want to set

USE_GNU_READLINE=yes

and include readline/builtin.mk instead

Are you seeing readline links in the buildlink tree?

I suspect that if configure looks for things manually, rather than
doing test compiles, it may look in the main fs rather than the
buildlink tree.  (This would be arguably buggy of it, and
cross-unfriendly.)

-- 
        Greg Troxel <gdt@ir.bbn.com>