[oe] How to properly enforce an ARM OABI build?

[Khem Raj]

>  The question now is - how could this be solved cleanly in Angstrom?
>
>  Would this be an option:
>  TARGET_OS ?= "${@['${TARGET_OS_UC}', 'uclinux-uclibc'][bb.data.getVar('TARGET_ARCH',d)  in ['bfin']]}"
>

looks ok.