Strange build error on port evbarm64

[Paul Goyette <paul%whooppee.com@localhost>]

While trying to make sure I haven't broken anything, I've been building
the same 67 builds as the releng cluster, on my pgoyette-compat branch.
I get the same success/failure as the releng cluster, which tells me
that my changes are unlikely to produce a build failure.

With one exception - the evbarm-aarch64 build...

I consistently get the following failure during the "release" target
(this is with build.sh's noise level set to 3, so I can see the actual
command that fails):

/build/netbsd-compat/tools/x86_64/evbarm64/bin/aarch64--netbsd-install -c -r -m 444 bootaa64.efi /build/netbsd-compat/release/evbarm/installation/misc
aarch64--netbsd-install: /build/netbsd-compat/release/evbarm/installation/misc.inst.8ySV7u: mkstemp: No such file or directory

The error message would seem to indicate that the directory
$RELEASEDIR/release/evbarm/installation does not exist, thus mkstemp
cannot create the new temp file misc.inst.* within the directory.

Of course, the exact file name varies from build to build, but the
failure occurs in the same place, every time.  And the failure occurs
regardlesss of j=1 vs j=12, and it occurs whether or not I have
-V MKDEBUG=yes defined.  Yet the releng build succeeds.  The only
remaining (significant) difference I can see is my use of

	-O ..../obj/evbarm64
  vs	-M ..../evbarm-aarch64/201810160500Z-obj

I do not specify the stuff for reproducible builds, but that should not
matter (famous last words?).

	-P -B 201810160500Z -V NETBSD_OFFICIAL_RELEASE=no

I can provide the entire log file (with noise-level=3) if it would be
helpful.  Here is the log header, along with a bit more context around
the eventual failure:

===> build.sh command:    ./build.sh -T /build/netbsd-compat/tools/x86_64/evbarm64 -D /build/netbsd-compat/dest/evbarm64 -O /build/netbsd-compat/obj/evbarm64 -R /build/netbsd-compat/release -V RELEASEMACHINEDIR=evbarm64 -V MKDEBUG=yes -V MKKDEBUG=no -U -N3 -m evbarm64 -j1 release
===> build.sh started:    Wed Oct 17 02:04:05 UTC 2018
===> NetBSD version:      8.99.25
===> MACHINE:             evbarm
===> MACHINE_ARCH:        aarch64
===> Build platform:      NetBSD 8.99.25 amd64
===> HOST_SH:             /bin/sh
===> MAKECONF file:       /etc/mk.conf
===> TOOLDIR path:        /build/netbsd-compat/tools/x86_64/evbarm64
===> DESTDIR path:        /build/netbsd-compat/dest/evbarm64
===> RELEASEDIR path:     /build/netbsd-compat/release
===> Updated makewrapper: /build/netbsd-compat/tools/x86_64/evbarm64/bin/nbmake-evbarm64
...
release ===> etc/evbarm/cdroms/installcd
cd /build/netbsd-compat/src/sys/stand/efiboot/bootaa64 && /build/netbsd-compat/tools/x86_64/evbarm64/bin/nbmake release
rm -f machine &&  ln -s /build/netbsd-compat/src/sys/stand/efiboot/bootaa64/../../../arch/evbarm/include machine
if [ -d /build/netbsd-compat/src/sys/stand/efiboot/bootaa64/../../../arch/aarch64/include ]; then  rm -f aarch64 && ln -s /build/netbsd-compat/src/sys/stand/efiboot/bootaa64/../../../arch/aarch64/include aarch64;  fi
if [ -d /build/netbsd-compat/src/sys/stand/efiboot/bootaa64/../../../arch/evbarm/include ]; then  rm -f evbarm && ln -s /build/netbsd-compat/src/sys/stand/efiboot/bootaa64/../../../arch/evbarm/include evbarm;  fi
if [ -d /build/netbsd-compat/src/sys/stand/efiboot/bootaa64/../../../arch/arm/include ]; then  rm -f arm && ln -s /build/netbsd-compat/src/sys/stand/efiboot/bootaa64/../../../arch/arm/include arm;  fi
true
/build/netbsd-compat/tools/x86_64/evbarm64/bin/aarch64--netbsd-install -c  -r -m 444 bootaa64.efi  /build/netbsd-compat/release/evbarm/installation/misc
aarch64--netbsd-install: /build/netbsd-compat/release/evbarm/installation/misc.inst.8ySV7u: mkstemp: No such file or directory
*** [release] Error code 1

Any help you can provide on identifying why I cannot get a successful 
build.sh release would be appreciated!


+------------------+--------------------------+----------------------------+
| Paul Goyette     | PGP Key fingerprint:     | E-mail addresses:          |
| (Retired)        | FA29 0E3B 35AF E8AE 6651 | paul at whooppee dot com   |
| Kernel Developer | 0786 F758 55DE 53BA 7731 | pgoyette at netbsd dot org |
+------------------+--------------------------+----------------------------+