Buildworld failure in sys/boot/efi/loader/main.c if WITHOUT_ZFS is defined

[Oleg V. Nauman]

===> sys/boot/efi/loader (all)
cc -target x86_64-unknown-freebsd12.0 --
sysroot=/usr/obj/usr/src/tmp -B/usr/obj/usr/src/tmp/usr/bin  -O2 
-pipe -march=nehalem  -
I/usr/src/sys/boot/efi/loader/../../../../lib/libstand -fPIC -
DTERM_EMU -I/usr/src/sys/boot/efi/loader -
I/usr/src/sys/boot/efi/loader/arch/amd64 -
I/usr/src/sys/boot/efi/loader/../include -
I/usr/src/sys/boot/efi/loader/../include/amd64 -
I/usr/src/sys/boot/efi/loader/../../../contrib/dev/acpica/include 
-I/usr/src/sys/boot/efi/loader/../../.. -
I/usr/src/sys/boot/efi/loader/../../i386/libi386 -DNO_PCI -DEFI 
-DSMBIOS_SERIAL_NUMBERS -DBOOT_FORTH -
I/usr/src/sys/boot/efi/loader/../../ficl -
I/usr/src/sys/boot/efi/loader/../../ficl/amd64 -
DLOADER_DISK_SUPPORT -DLOADER_GPT_SUPPORT -DLOADER_MBR_SUPPORT -
DLOADER_GELI_SUPPORT -fPIC -I/usr/src/sys/boot/ficl -
I/usr/src/sys/boot/ficl/amd64  -
I/usr/src/sys/boot/ficl/../common -
I/usr/src/sys/boot/efi/loader/../../common -ffreestanding -
Wformat -mno-mmx -mno-sse -mno-avx -msoft-float -fshort-wchar -
mno-red-zone -mno-aes -g -MD  -MF.depend.main.o -MTmain.o -
std=gnu99 -Wsystem-headers -Werror -Wall -Wno-format-y2k -W -
Wno-unused-parameter -Wstrict-prototypes -Wmissing-prototypes -
Wpointer-arith -Wno-uninitialized -Wno-pointer-sign -Wno-empty-
body -Wno-string-plus-int -Wno-unused-const-variable -Wno-
tautological-compare -Wno-unused-value -Wno-parentheses-equality 
-Wno-unused-function -Wno-enum-conversion -Wno-unused-local-
typedef -Wno-address-of-packed-member -Wno-format -Qunused-
arguments  -c /usr/src/sys/boot/efi/loader/main.c -o main.o
/usr/src/sys/boot/efi/loader/main.c:883:8: error: implicit 
declaration of function
      'efizfs_get_handle_by_guid' is invalid in C99 [-Werror,-
Wimplicit-function-declaration]
                            efizfs_get_handle_by_guid(z_dev-
>pool_guid);
                            ^
/usr/src/sys/boot/efi/loader/main.c:883:8: error: this function 
declaration is not a prototype
      [-Werror,-Wstrict-prototypes]
/usr/src/sys/boot/efi/loader/main.c:883:39: error: incomplete 
definition of type 'struct zfs_devdesc'
                            efizfs_get_handle_by_guid(z_dev-
>pool_guid);
                                                      ~~~~~^
/usr/src/sys/boot/efi/loader/main.c:875:10: note: forward 
declaration of 'struct zfs_devdesc'
                struct zfs_devdesc *z_dev;
                       ^
3 errors generated.
*** Error code 1

Stop.
make[6]: stopped in /usr/src/sys/boot/efi/loader
*** Error code 1