[yocto] Fwd: Preventing rebuild of dependencies

[Sassan Panahinejad]

Hi,

On several Yocto-based projects I've worked on, I've ended up accidentally
triggering rebuilds of large packages such as QT or Chromium.

The example I keep running into at the moment is whenever I modify the
kernel config, I trigger Chromium to rebuild next time I rebuild the image.
This means losing as much as 4 hours every time.

When searching for a solution, I found other posts and the workaround
usually given is not to rebuild the image after kernel changes and copy the
kernel manually. That's all very well, but I'm also making changes to other
parts of the system and therefore need to be able to rebuild the image
without waiting for Chromium to compile.

The problem seems to come down to one of Chromium's deps depending on the
kernel for some headers. Now naturally changes to a dependency results in a
rebuild, but I the operator know that the change in question will not have
any affect.

I'd like to just be able to blacklist rebuilding of Chromium and QT, but I
can't find a way other than sticking in some fake rules in the Chromium
recipe. In buildroot, one could often cheat by touching the relevant stamp
file to make it think it had rebuilt. Is the same possible in Yocto?

Note: sstate-cache is enabled.

Thanks
Sassan Panahinejad
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