i386 Xen integration breaks linking NET4501 kernel

["John D. Baker" <jdbaker%consolidated.net@localhost>]

A recent build of -current/i386 fails when trying to link a kernel built
from the NET4501 config:

[...]
#      link  NET4501/netbsd
/r0/build/current/tools/amd64/bin/i486--netbsdelf-ld -Map netbsd.map --cref -T netbsd.ldscript -Ttext c0100000 -e start -X -o netbsd ${SYSTEM_OBJ:[@]:Nswapnetbsd.o} ${EXTRA_OBJ} vers.o swapnetbsd.o
/r0/build/current/tools/amd64/bin/i486--netbsdelf-ld: locore.o: in function `start_xenpvh':
(.text+0x410): undefined reference to `hvm_start_paddr'
/r0/build/current/tools/amd64/bin/i486--netbsdelf-ld: (.text+0x436): undefined reference to `HYPERVISOR_shared_info_pa'
*** [netbsd] Error code 1

nbmake: stopped in /r0/build/current/obj/i386/sys/arch/i386/compile/NET4501
1 error

nbmake: stopped in /r0/build/current/obj/i386/sys/arch/i386/compile/NET4501

ERROR: Failed to make all in "/r0/build/current/obj/i386/sys/arch/i386/compile/NET4501"
*** BUILD ABORTED ***

-- 
|/"\ John D. Baker, KN5UKS               NetBSD     Darwin/MacOS X
|\ / jdbaker[snail]consolidated[flyspeck]net  OpenBSD            FreeBSD
| X  No HTML/proprietary data in email.   BSD just sits there and works!
|/ \ GPGkeyID:  D703 4A7E 479F 63F8 D3F4  BD99 9572 8F23 E4AD 1645