runqemu is looking for the QB_DEFAULT_KERNEL to be set to "none"
to trigger special processing. The current set of QB_DEFAULT_KERNEL=""
won't trigger that behaviour .. so we change the default.
We also make the assignments weak, to allow easier overrides in
specific implementations.
We also need a patch to qemuboot.bbclass to make the defaults ??=,
and when that is done, our ?= here will work properly.
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>
2f22425222