ocaml 4.02.2 won't build on Snow Leopard

[Peter Hancock]

Before I write a ticket, I wonder if anyone else has had problems in gettin ocaml at 4.02.2 to build.
This is on an early MacBook1,1, with OSX 10.6.8, Xcode 3.2.4.

The occasion of the error in the log file seems to be

   ld: absolute addressing (perhaps -mdynamic-no-pic) used in _caml_system__code_begin
   from i386.pic.o not allowed in slidable image.
   Use '-read_only_relocs suppress' to enable text relocs:

Mind you, near the start there's a warning:

   :info:configure [WARNING] The environment variable MACOSX_DEPLOYMENT_TARGET is set.
   :info:configure  This will probably prevent compiling the OCaml system.

Where might this variable be being set?  Is it really causing the problem?

I might mention that this version of ocaml built fine on a late 2012 Mini running 10.10.3

-- 
Peter Hancock