Not able to compile GENERIC kernel

[mfv]

Hello,

After rebuilding FreeBSD for many years I am not able to build a GENERIC 
kernel for the last few days.   It always stops when compiling acpi.

The source code is up to date for 7 -STABLE for i386 on a amd64 cpu.  I 
have always been able to recompile a GENERIC kernel since release 5.1 
and do not know what I am doing wrong.

Any help would be greatly appreciated.

With thanks.

Marek

The following is the tail end of "make buildkernel":

cc -O2 -fno-strict-aliasing -pipe -D_KERNEL -DKLD_MODULE -std=c99 -
nostdinc -I /usr/src/sys/modules/acpi/acpi/../../../contrib/dev/acpica
-DHAVE_KERNEL_OPTION_ HEADERS -include
/usr/obj/usr/src/sys/GENERIC/opt_global.h -I. -I@ -I@/contrib/a ltq
-finline-limit=8000 --param inline-unit-growth=100 --param large-
function-growth=1000 -fno-common -g -I/usr/obj/usr/src/sys/GENERIC
-mno-align-long-strings -mpreferred-stack-boundary=2 -mno-mmx -mno-3dnow
-mno-sse -mno-sse2 -mno-sse3 - ffreestanding -Wall -Wredundant-decls
-Wnested-externs -Wstrict-prototypes -Wmi ssing-prototypes -Wpointer-
arith -Winline -Wcast-qual -Wundef -Wno-pointer-sign -fformat-extensions 
-c /usr/src/sys/modules/acpi/acpi/../../../i386/acpica/acpi _machdep.c
@ ->/usr/src/sys
ln: @/sys: Operation not permitted
*** Error code 1

Stop in /usr/src/sys/modules/acpi/acpi.
*** Error code 1

Stop in /usr/src/sys/modules/acpi.
*** Error code 1

Stop in /usr/src/sys/modules.
*** Error code 1

Stop in /usr/obj/usr/src/sys/GENERIC.
*** Error code 1

Stop in /usr/src.
*** Error code 1

Stop in /usr/src.

[root] /usr/src #