cmake help for py-gdal

[Greg Troxel <gdt%lexort.com@localhost>]

py-gdal is failing to build on i386.  The problem is that cmake, as
invoked manually, is failing to build the 64-bit atomic test program.

But, really the problem is that py-gdal's makefile wants to do a
slightly odd build in a subdir.  It's not using cmake/build.mk, and I
suspect stuff is getting lost.    Really, this should be cleaned up and
then we can see where we are.

The build recipe is

        pre-build:
                cd ${WRKSRC} && mkdir build && cd build && \
                cmake ${CMAKE_CONFIGURE_ARGS} .. && \
                cd swig/python && \
                ${MAKE} python_generated_files

and then the actual build is setuptools.

I am asking for help from a cmake expert.   What's the right way to do
this?

I'm guessing it's post-configure to do swig or maybe the cmakefiles are
ok and it's just specifying a subdir.