[U-Boot] without board level config.mk How to add CPPFLAGS

[zzs]

> > > > So I want add "-iquote my/header/dir" to CPPFLAGS
> > >
> > > This will not be accepted.
> > >
> > Does this means that there are no way to append custom cpp flags to
> > CPPFLAGS ?
>
> No, it means that your approach to include out-of-tree files has been
> rejected.  Nothing more and not less.
>
And then how to do that thing : Append custom cpp flags to CPPFLAGS ?

e.g. -Wcomments

And after append them to CPPFLAGS, Does these flags appear in CFLAGS
auto automatically ?

-- 
Best Regards,
zzs