buildtools-tarball/uninative-tarball: Fix for working with populate_sdk under sstate...

buildtools-tarball/uninative-tarball: Fix for working with populate_sdk under sstate control

Firstly, these recipes are not target (MACHINE) specific so they should
by SDK_ARCH based, not PACKAGE_ARCH.

Also fix use of SDK_DEPLOY -> SDKDEPOLYDIR after other recent changes.

Together these fixes avoid various build failures and ensure the tarballs
only get built once rather than multiple times.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>