[S] Change in coreboot[main]: xcompile: Add -Wextra with temporary exceptions

[Felix Singer (Code Review)]

Attention is currently required from: Elyes Haouas, Martin L Roth.

Felix Singer has posted comments on this change by Felix Singer. ( https://review.coreboot.org/c/coreboot/+/83347?usp=email )

Change subject: xcompile: Add -Wextra with temporary exceptions
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Patch Set 3:

(1 comment)

Patchset:

PS3:
> I would have done the opposite.
> "Wextra" may evolve with new options which may generate compilation errors in the future.

I wouldn't worry about new warnings in Wextra. We test new toolchains long enough before we introduce them. So we can just disable or even fix new warnings beforehand.
> On the other hand, activating the options individually seems more appropriate to me.
> Once you have covered all of the "Wextra" options, you can activate it.

The advantage here is that all other options from Wextra are already active, which wouldn't be the case with enabling each option separately. So only some problematic ones are disabled and we know exactly which are failing.