Problem building a release of aarch64

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

I've managed to get clean builds on my [pgoyette-compat] branch from 66
out of the 67 architectures that are currently being built by the releng
build cluster.  The only one that isn't working is aarch64.

It seems to get all the way through building the world, but it fails at
this point:

...
release ===> etc/evbarm/instkernel/sshramdisk
release ===> etc/evbarm/instkernel/instkernel
test -z "" ||  /build/test/tools/x86_64/evbarm64/bin/aarch64--netbsd-install -r -p -c -m 444    /build/test/release/evbarm64/installation/instkernel
release ===> etc/evbarm/cdroms
release ===> etc/evbarm/cdroms/installcd
cd /build/test/src/sys/stand/efiboot/bootaa64 && /build/test/tools/x86_64/evbarm64/bin/nbmake release
/build/test/tools/x86_64/evbarm64/bin/aarch64--netbsd-install -c -p -r 
-m 444 bootaa64.efi  /build/test/release/evbarm/installation/misc
aarch64--netbsd-install: /build/test/release/evbarm/installation/misc.inst.sJgZbU: mkstemp: No such file or directory
*** [release] Error code 1

Thinking that I might have broken something, I checked out sources from
MAIN, at the point of my most recent sync-with-head.  (This corresponds
to tag pgoyette-compat-0930, very close to 2018-09-30 at 00:00 UTC.)
And sure enough, a build of the MAIN branch at that time-stamp fails in
the same manner.

I had seen similar failures earlier, for some of the evbearm's, and I
traced those down to an accidental use of MKKDEBUG (which turns on -g
for gcc compiles, which makes things a lot bigger).  But I've checked
my logs and confirmed that MKKDEBUG is no longer enabled, and the only
kernel source being compiled with -g is debugsyms.o

Does anyone have any additional clues as to what might be going wrong?

FWIW, here's my build.sh command:

	cd /build/test/src
	./build.sh \
		-T /build/test/tools/x86_64/evbarm64 \
		-D /build/test/dest/evbarm64 \
		-O /build/test/obj/evbarm64 \
		-R /build/test/release \
		-V RELEASEMACHINEDIR=evbarm64 \
		-V MKDEBUG=no \
		-V MKKDEBUG=no -U -m evbarm64 \
		-j1 release


And the /build/test/src sources were checked out from anoncvs using

	cvs update -r pgoyette-compat-0930


+------------------+--------------------------+----------------------------+
| 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 |
+------------------+--------------------------+----------------------------+