Build broken when MKDEBUG=yes

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

An amd64 build (on a 9.99.73 NetBSD-amd64 host) fails when building with
-V MKDEBUG=yes  Here's the error detail:

...
install ===> tests/net/if_tap
#   install  /build/netbsd-compat/dest/amd64/usr/libdata/debug/usr/tests/net/if_tap/rump_open_tap.debug
/build/netbsd-compat/tools/x86_64/amd64/bin/x86_64--netbsd-install -U -M /build/netbsd-compat/dest/amd64/METALOG -D /build/netbsd-compat/dest/amd64 -h sha256 -N /build/netbsd-compat/src_ro/etc -c -p -r -o root -g wheel -m 444  rump_open_tap.debug /build/netbsd-compat/dest/amd64/usr/libdata/debug/usr/tests/net/if_tap/rump_open_tap.debug
x86_64--netbsd-install: /build/netbsd-compat/dest/amd64/usr/libdata/debug/usr/tests/net/if_tap/rump_open_tap.debug.inst.nKLa0w: mkstemp: No such file or directory
*** [/build/netbsd-compat/dest/amd64/usr/libdata/debug/usr/tests/net/if_tap/rump_open_tap.debug] Error code 1
nbmake[7]: stopped in /build/netbsd-compat/src_ro/tests/net/if_tap
1 error
nbmake[7]: stopped in /build/netbsd-compat/src_ro/tests/net/if_tap
<EOF>

(Also reported to roy@ on IRC)


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