[oe] RFC: When PREFERRED_PROVIDER does not build, don't try other alternatives by default

[Koen Kooi]

Rod Whitby wrote:
> Whenever I build virtual/kernel, and for some reason (perhaps a git
> fetcher problem, or a patch doesn't apply cleanly) it doesn't build,
> bitbake decides to then go and build every other kernel under the sun
> trying to complete virtual/kernel.
>
> This is undesirable to the extreme,

Related to that: if for some reason you add a linux-myleetmachine.bb 
recipe instead of extending existing kernel recipes, please set 
COMPATIBLE_MACHINE = "myleetmachine" inside that recipe.
The same goes for other machine specific recipes (e.g. omapfbplay_git.bb 
should have COMPATIBLE_MACHINE set to all omap3 boards).

regards,

Koen