augmenting the standard include path

[scs at eskimo dot com (Steve Summit)]

I'm trying to build a cross-compiler (for an arm-based raspberry
pi, if it matters), and I think I need to tell it to also search
(in effect) /usr/include/arm-linux-gnueabihf/ for machine-specific
header files.  But I'm not sure how to.

I've copied the target system's exact header tree into
/usr/local/rpi/usr/local/include on my build machine.
And my fledgling cross-compiler, which I configured with
--with-sysroot=/usr/local/rpi, seems to be finding them there.
But the copy of stdio.h there has the line

	#include <bits/predefs.h>

in it, and that's *not* getting found, because it's in
/usr/include/arm-linux-gnueabihf/bits/ on the target system, or in
/usr/local/rpi//usr/include/arm-linux-gnueabihf/bits/ on my build
machine.

So if the native gcc on the target system knows to search there,
how do I teach my cross-compiler to search there, too?

Thanks in advance.