build system doesnt properly detect applet rebuild requirement

[Bernhard Fischer]

On Sat, Feb 03, 2007 at 02:44:07AM -0500, Mike Frysinger wrote:
>$ make distclean
>$ make allnoconfig
>$ make menuconfig
>-> enable dmesg, syslog, klogd, logger
>$ make
>$ nano .config
>-> disable syslog, klogd, logger
>$ make oldconfig
>$ make
><link failure due to applets.o still wanting syslog/klogd/logger _main funcs>
>-mike

Confirmed. See also vda's note that it's disfunctional:
http://busybox.net/lists/busybox/2007-January/025966.html

In the old buildsys we had a dependency like
applets.o: .config

Nowadays applets.o depends on usage_compressed.h alone.
Iff the problem turns out to be passing -include autoconf.h directly
(so, perhaps, autoconf.h isn't listed in foo.d as dep), then putting an
#include "autoconf.h" into libbb.h would perhaps change that
misbehaviour. Any takers?