[Buildroot] How do I select the PCMCIA package ?

[mike]

Simple question. How do I select the PCMCIA package? What do I need to
select first ?

I want to build a system with PCMCIA, but menuconfig doesn't allow it
for selection.
It seems to be dependent on BR2_PACKAGE_LINUX, and the only way I can
see of getting that set is by selecting something in "Board Support
Options" - none of which I really want.
I have built my own "special" version of the linux kernel with the
various drivers and things I want and set $(LINUX_DIR) and
$(LINUX_SOURCE_DIR) to point to the right place. Are there other
undocumented environment variables I need to set up ?

Mike