freebsd stable - Jan 2018 - why does buildworld fail on stable/11 ?

I tried asking for help on this several days ago on freebsd-questions@,
but got no responses.  I'm trying freebsd-stable@ next because it involves
trying to build world on a 11.1-STABLE system from a freshly checked out,
unaltered source tree at r328251.  The system currently installed is from a
11.1-STABLE installer image:

FreeBSD hellas 11.1-STABLE FreeBSD 11.1-STABLE #0 r326620: Wed Dec  6 15:08:03
UTC 2017     root at releng2.nyi.freebsd.org:/usr/obj/usr/src/sys/GENERIC  amd64

I would like to keep it reasonably up to date, but I am stumped.
     I did a fresh svn checkout into a completely empty /usr/src, but when
I tried to run a "make buildworld", it failed like this.

Script started on Mon Jan 22 02:11:21 2018
hellas#	setenv CCACHE_DIR /buildwork/ccache.freebsd
hellas#	cd /usr/src
hellas#	date && \
? time nice +11 make buildworld  && date
Mon Jan 22 02:13:05 CST 2018
Unknown modifier 'U'

Unknown modifier 'U'

Unknown modifier 'U'

Unknown modifier 'U'

Unknown modifier 'U'

Unknown modifier 'U'

Unknown modifier 'U'

Unknown modifier 'U'

Unknown modifier 'U'

Unknown modifier 'U'

Unknown modifier 'U'

Unknown modifier 'U'

Unknown modifier 'U'

Unknown modifier 'U'

Unknown modifier 'U'

Unknown modifier 'U'

Unknown modifier 'U'

Unknown modifier 'U'

Unknown modifier 'U'

Unknown modifier 'U'

Unknown modifier 'U'

Unknown modifier 'U'

Unknown modifier 'U'

Unknown modifier 'U'

"/usr/src/share/mk/src.sys.mk", line 28: Option DIRDEPS_BUILD may only
be defined in , environment, or make argument, not /etc/src.conf.
*** Error code 1

Stop.
make: stopped in /usr/src
0.035u 0.047s 0:01.65 4.2%	15254+422k 88+21io 31pf+0w
hellas#	exit
exit

Script done on Mon Jan 22 02:13:19 2018

Note that 'U' has not always been the letter complained of in the
"Unknown
modifier" messages.  The content of /etc/src.conf is as follows.

PORTS_MODULES=multimedia/cuse4bsd-kmod sysutils/pefs-kmod
emulators/virtualbox-ose-kmod net/ndproxy
WITH_LLDB=yes
#WITH_FAST_DEPEND=yes
WITH_CCACHE_BUILD=yes

As you can see, there is no DIRDEPS_BUILD in /etc/src.conf.  I don't even
know what DIRDEPS_BUILD is.
     Anyway, I'm stuck.  Can someone please tell me what is going wrong and
how to fix it?  I'd really like to be able to update my system, not only to
keep it reasonably current, but also to be able to customize a kernel.  Thanks
in advance for any suggestions/solutions.


                                  Scott Bennett, Comm. ASMELG, CFIAG
**********************************************************************
* Internet:   bennett at sdf.org   *xor*   bennett at freeshell.org  *
*--------------------------------------------------------------------*
* "A well regulated and disciplined militia, is at all times a good  *
* objection to the introduction of that bane of all free governments *
* -- a standing army."                                               *
*    -- Gov. John Hancock, New York Journal, 28 January 1790         *
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On 22/01/2018 09:17, Scott Bennett wrote:
>     Anyway, I'm stuck.  Can someone please tell me what is going wrong
and
> how to fix it?  I'd really like to be able to update my system, not
only to
> keep it reasonably current, but also to be able to customize a kernel. 
Thanks
> in advance for any suggestions/solutions.
Hi,

What I'd do is firstly to make things as simple as possible. First do
the upgrade simply. Either delete or call make.conf & src.conf something
else. Then get a fresh src  and ports tree via svnlite. Then do

rm -rf /buildwork/ccache.freebsd
mkdir /buildwork/ccache.freebsd

then

[/usr/src #] make cleandir && make clean && make buildworld
&& make
buildkernel && make installkernel && mergemaster -p

[make changes if needed]

[/usr/src #] make installworld && mergemaster

[make more changes if needed]

reboot

then cd into /usr/src as root, then do

yes | make delete-old
yes | make delete-old-libs

reboot again

then re-enable your extra lines in make.conf and src.conf, if you need them.

It may be down to something in the ccache dir, I guess.

-- 
J.