Christmas wish list: -Werror and -Wno-warn-about-X

["Herbert, Marc" <marc.herbert@intel.com>]

> Anyway, with this it was very easy to reproduce and find the cause.
> Fixed and pushed, so mainline Sparse should be OK now.

> Many thanks for the bug report,

Fix confirmed, many thanks for the super quick fix!

It's also great to see that you seem to have more time to spend on
sparse right now. So trying to push my luck, here's the number 1 item on
my "Christmas Wish List": a combination of -Werror and -Wno-warn-about-X
options that would provides finer-grained and generally better control
on the exit status and output. After maintaining sparse automation for
many months, this is I think what would lower the CI adoption bar the
most.

So far we've been using a brittle script that captures the incredibly
verbose and mostly unusable output (mostly due to some hard-to-fix
warnings located in common .h files) and "post-processes" it
with... "grep".
 https://github.com/thesofproject/sof/commit/b7708182fbe5d

I'm curious how people typically automate runnning sparse on the
Linux kernel. Does everyone "greps" logs too? Or is it more like
`$(wc -l) == 0`?