HEAD buildkernel error (aic7xxx_seq.h is missing. Run 'make ahcfirmware')

[Luigi Rizzo]

on a freshly checked out HEAD,
"make toolchain" followed by "make buildkernel" fails at this stage:

	...
	@ -> /usr/home/luigi/FreeBSD/head/sys
	machine -> /usr/home/luigi/FreeBSD/head/sys/amd64/include
	x86 -> /usr/home/luigi/FreeBSD/head/sys/x86/include
	Error: aic7xxx_reg_print.c is missing.  Run 'make ahcfirmware'
	Error: aic7xxx_seq.h is missing.  Run 'make ahcfirmware'
	Error: aic7xxx_reg.h is missing.  Run 'make ahcfirmware'

(don't think it matters, but i am cross compiling amd64
from a stable/9 amd64 system, using clang).
I am not sure which commit triggered the problem,
but this used to work in the past -- toolchain was enough
to build a kernel.

cheers
luigi