Bitbake recipes requiring configuration

[Joel Stanley]

Hi Brad,

I'm after some general direction for bitbake recipes that require a
machine to provide configuration or script. eg:

SRC_URI += "file://whiz-bang.sh"

whiz-app/
  whiz-app.bb
  amachine/whiz-bang.sh
  theothermachine/whiz-bang.sh

If my layer supports three machines: amachine, theothermachine, and
bestmachine, bitbake will emit a warning for bestmachine, because
there's no whiz-bang.sh specified.

We could change the SRC_URI to be conditional on :append:<machine>, or
provide an whiz-bang.sh next to the .bb. Or another option I haven't
thought of.

Is there a (better) pattern we should be following here?

For a concrete case, I have put this change up for review:

  https://gerrit.openbmc-project.xyz/c/openbmc/openbmc/+/53432

There are several apps in meta-ibm that currently warn depending on
the machine you're targeting, so would benefit from cleaning this up.

Cheers,

Joel