USE_CMAKE in meta-pkgs/kde4/kde4.mk

[Brook Milligan <brook@viola.i-did-not-set--mail-host-address--so-tickle-me>]

I am building a package that depends on kde4 and therefore should
presumably include kde4.mk.  That file defines many CMAKE_ARGS options,
yet does not define USE_CMAKE.  It seems to me that it should in order
to ensure that cmake is actually used.  As it currently stands,
individual packages must do this each time.

Thoughts?

Cheers,
Brook