[PATCH v4 3/4] rust: add a Kconfig function to test for support of bindgen options

[Asuna Yang]

On 11/24/25 9:48 AM, Miguel Ojeda wrote:
> More importantly, should we just have a separate function for backend
> flags? That would be easier and would avoid having to use the
> environment variable, if I understand the commit message here
> correctly. And, anyway, it is actually the only function we need so
> far.

You are right, separated might be better.

Another reason is, in `scripts/Makefile.compiler`, there is a set of 
functions with the same name provided for use by Makefile. Since we 
currently do not need to check for bindgen options in Makefile, I didn't 
add function for bindgen there. If we add it in the future, the 
`bindgen-option` function in `Kconfig.include` will correspond to the 
`bindgen-option-yn` function in `Makefile.compiler`, and 
`bindgen-option` function in `Makefile.compiler` will return the 
selected option instead of yn.

If we don't separate them now, for consistency, in `Makefile.compiler`, 
`$(call bindgen-option,-- --some-flag-a,-- --some-flag-b)` will return 
an option prefixed with --, which makes it difficult to use.

I will separate them into two functions in the next revision, 
`bindgen-option` and `bindgen-backend-option` (or `bindgen-cc-option`? 
Which one do you prefer?).