port-arm/52785: Linux DTS unpriv. build failure (arm-port?)

[bch <brad.harder%gmail.com@localhost>]

>Number:         52785
>Category:       port-arm
>Synopsis:       dts build failure w/ unpriviledged build
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    port-arm-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Dec 04 05:05:00 +0000 2017
>Originator:     bch <brad.harder%gmail.com@localhost>
>Release:        NetBSD 8.99.8
>Organization:
	method logic digital
>Environment:
System: NetBSD kamloops 8.99.8 NetBSD 8.99.8 (GENERIC) #81: Sun Dec 3
10:36:46 PST 2017
root@kamloops:/usr/obj/sys/arch/amd64/compile/GENERIC amd64
Architecture: x86_64
Machine: amd64
>Description:
	Linux Device-tree symlink/installation failure during non-priveleged
(release) build.

build invocation (from /usr/src):

nice ./build.sh  -j1 -u -U -T
/home/bch/usr/obj_nanopi/tooldir.NetBSD-8.99.7-amd64 -D
/home/bch/arm_destdir -R /home/bch/releasedir -O
/home/bch/usr/obj_nanopi/ -m evbearmv7hf-el release ; # distribution
sets release


output:


...
checkflist ===> distrib/sets
cd /usr/src/distrib/sets &&  DESTDIR=/home/bch/arm_destdir
MACHINE=evbarm  MACHINE_ARCH=earmv7hf
AWK=/home/bch/usr/obj_nanopi/tooldir.NetBSD-8.99.7-amd64/bin/nbawk
CKSUM=/home/bch/usr/obj_nanopi/tooldir.NetBSD-8.99.7-amd64/bin/nbcksum
 DB=/home/bch/usr/obj_nanopi/tooldir.NetBSD-8.99.7-amd64/bin/nbdb
EGREP=grep\ -E  HOST_SH=/bin/sh
MAKE=/home/bch/usr/obj_nanopi/tooldir.NetBSD-8.99.7-amd64/bin/nbmake
MKTEMP=/home/bch/usr/obj_nanopi/tooldir.NetBSD-8.99.7-amd64/bin/nbmktemp
 MTREE=/home/bch/usr/obj_nanopi/tooldir.NetBSD-8.99.7-amd64/bin/nbmtree
 PAX=/home/bch/usr/obj_nanopi/tooldir.NetBSD-8.99.7-amd64/bin/nbpax
COMPRESS_PROGRAM=gzip  GZIP=-n
PKG_CREATE=/home/bch/usr/obj_nanopi/tooldir.NetBSD-8.99.7-amd64/bin/nbpkg_create
 SED=/home/bch/usr/obj_nanopi/tooldir.NetBSD-8.99.7-amd64/bin/nbsed
TSORT=/home/bch/usr/obj_nanopi/tooldir.NetBSD-8.99.7-amd64/bin/nbtsort\
-q  /bin/sh /usr/src/distrib/sets/checkflist  -L base  -M
/home/bch/arm_destdir/METALOG.sanitised
make distribution started at:  Sun Dec  3 20:04:15 PST 2017
make distribution finished at: Sun Dec  3 20:12:11 PST 2017
release ===> etc        (with: DISTRIBUTION_DONE=1)
cd /usr/src/sys/arch/evbarm/conf &&
/home/bch/usr/obj_nanopi/tooldir.NetBSD-8.99.7-amd64/bin/nbconfig  -s
/usr/src/sys  -U DEBUG -b
/home/bch/usr/obj_nanopi/sys/arch/evbarm/compile/ARMADAXP ARMADAXP
Build directory is /home/bch/usr/obj_nanopi/sys/arch/evbarm/compile/ARMADAXP
Don't forget to run "make depend"
/home/bch/usr/obj_nanopi/tooldir.NetBSD-8.99.7-amd64/bin/nbmake -C
/home/bch/usr/obj_nanopi/sys/arch/evbarm/compile/ARMADAXP depend &&
/home/bch/usr/obj_nanopi/tooldir.NetBSD-8.99.7-amd64/bin/nbmake -C
/home/bch/usr/obj_nanopi/sys/arch/evbarm/compile/ARMADAXP
ln: dts/arm/dts: Permission denied
*** Failed target:  .BEGIN
*** Failed command: ln -sf
/usr/src/sys/external/gpl2/dts/dist/arch/arm/boot/dts dts/arm
*** Error code 1
Stop.
nbmake[2]: stopped in /home/bch/usr/obj_nanopi/sys/arch/evbarm/compile/ARMADAXP
*** [kern-ARMADAXP] Error code 1
nbmake[1]: stopped in /usr/src/etc
1 error
nbmake[1]: stopped in /usr/src/etc
*** [release] Error code 2

nbmake: stopped in /usr/src
1 error
...


>How-To-Repeat:
$ cd /usr/src
$ nice ./build.sh  -j1 -u -U -T
/home/bch/usr/obj_nanopi/tooldir.NetBSD-8.99.7-amd64 -D
/home/bch/arm_destdir -R /home/bch/releasedir -O
/home/bch/usr/obj_nanopi/ -m evbearmv7hf-el release ; # distribution
sets release
>Fix: