# dmesg | grep acpiwmibus
acpiwmibus at acpiwmi0 not configured

# egrep acpiwmibus /usr/src/sys/arch/amd64/conf/GIFT
acpiwmibus*     at acpiwmi?             # ACPI WMI Bus support
wmidell*        at acpiwmibus?          # Dell WMI mappings
wmieeepc*       at acpiwmibus?          # Asus Eee PC WMI mappings
wmihp*          at acpiwmibus?          # HP WMI mappings
wmimsi*         at acpiwmibus?          # MSI WMI mappings

# ./build.sh -O /usr/obj -T /usr/tools kernel=GIFT
[...]
===> Build directory:     /usr/obj/sys/arch/amd64/compile/GIFT
(cd /usr/obj/sys/arch/amd64/compile/GIFT && rm -f a.out [Ee]rrs mklog core *.core .gdbinit || true)
/usr/src/sys/arch/amd64/conf/GIFT:297: acpiwmibus*: unknown device `acpiwmibus'
*** Stop.

ERROR: nbconfig failed for GIFT
*** BUILD ABORTED ***