bootblocks compile broken?

# cd /sys/boot/i386
# make

[...]

cc -O2 -pipe  -DLOADER_NFS_SUPPORT -DCOMPORT=0x3f8 -DCOMSPEED=9600
-DSMBIOS_SERIAL_NUMBERS -DTERM_EMU -Dalloca=__builtin_alloca
-I/usr/src/sys/boot/i386/libi386/../../common
-I/usr/src/sys/boot/i386/libi386/../btx/lib
-I/usr/src/sys/boot/i386/libi386/../../../contrib/dev/acpica
-I/usr/src/sys/boot/i386/libi386/../../..
-I.
-I/usr/src/sys/boot/i386/libi386/../../../../lib/libstand/
-ffreestanding -mpref
-mno-sse -mno-sse2
-mno-sse3
-c /usr/src/sys/boot/i386/libi386/bootinfo64.c

/usr/src/sys/boot/i386/libi386/bootinfo64.c: In function 'bi_checkcpu':
/usr/src/sys/boot/i386/libi386/bootinfo64.c:155: error: 
'CENTAUR_VENDOR_ID' undeclared (first use in this function)
/usr/src/sys/boot/i386/libi386/bootinfo64.c:155: error: (Each 
undeclared identifier is reported only once
/usr/src/sys/boot/i386/libi386/bootinfo64.c:155: error: for each 
function it appears in.)
*** Error code 1

Stop in /usr/src/sys/boot/i386/libi386.
*** Error code 1

this is defined in specialreg.h
but in "machine/specialreg.h"
there is no 'machine' as such

I suspect that someone expected to only compile bootblocks as part of 
a system build?

not sure what the "correct" fix is..