[releng_4 tinderbox] failure on i386/i386

[Luoqi Chen]

> This is due to your latest change to src/sys/conf/Makefile.i386
> in RELENG_4.
> 
> The problem is that when compiling LINT, the DIAGNOSTIC option
> is defined in opt_global.h, and null_subr.c attempts to include
> opt_ddb.h which doesn't exist.  The version in HEAD (kern.*.mk)
> doesn't do this.  Is this change really necessary for PAE?
>
For options like PAE, it's crucial for the module build process
to see them, otherwise the compiled binaries are useless, which
defeats the purpose of building the modules along with the kernel.
That said, I probably shouldn't have lumped this change with the PAE
commit.

On the other hand, all modules should create all the opt_*.h files
it needs when built individually. Add opt_ddb.h to nullfs's Makefile
should fix the breakage.

-lq

> 
> Cheers,
> -- 
> Ruslan Ermilov		Sysadmin and DBA,
> ru at sunbay.com		Sunbay Software Ltd,
> ru at FreeBSD.org		FreeBSD committer
>