Trouble with math/lp_solve buildlink

Hi,

I'm trying to create a package using math/lp_solve

It has no buildlink3.mk file, so I tried to add a DEPENDS+= line to my 
package Makefile:

   DEPENDS+=    lp_solve>5.5:../../math/lp_solve

pkgsrc correctly figures out the dependency:

   => Full dependency lp_solve>5.5: found lp_solve-5.5.2.0

Unfortunately neither the header nor the library links are beeing 
created in work/.buildlink :

   [in configure stage]
   checking lpsolve/lp_lib.h usability... no
   checking lpsolve/lp_lib.h presence... no
   checking for lpsolve/lp_lib.h... no
   configure: error: lpsolve headers not found.

I must be doing something wrong but I think I've correctly followed the 
instructions of the pkgsrc developer's guide and I'm now a bit puzzled.

Any idea ?

-- 
Francois Tigeot

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