cross-build failure on objcopy

When cross-compiling for i386 on amd64 (which has 2 by 4 cores), I get
the error below after a previously successful build.

Running the build again (a 3rd time) completes successfully :-(

This is the output from

	cd /usr/src/release; ./release.sh -c release-i386.conf

 [ .. ]

===> usr.bin/cxxfilt (all)
===> usr.bin/objcopy (all)
===> usr.sbin/bsnmpd/tools/bsnmptools (all)
===> usr.bin/file2c (all)
===> usr.bin/gprof (all)
===> usr.bin/indent (all)
===> usr.bin/lex (all)
===> usr.bin/mkstr (all)
===> usr.bin/nm (all)
objcopy: open objcopy failed: Text file busy
--- objcopy ---
*** [objcopy] Error code 1
make[4]: *** objcopy removed

make[4]: stopped in /usr/local/release-builds/i386/usr/src/usr.bin/objcopy
.ERROR_TARGET='objcopy'
.ERROR_META_FILE='/usr/local/release-builds/i386/tmp/obj/usr/local/release-builds/i386/usr/src/amd64.amd64/usr.bin/objcopy/objcopy.meta'
.MAKE.LEVEL='4'
MAKEFILE=''
.MAKE.MODE='meta missing-filemon=yes missing-meta=yes silent=yes'
_ERROR_CMD='objcopy --strip-debug --add-gnu-debuglink=objcopy.debug
objcopy.full objcopy;'
.CURDIR='/usr/local/release-builds/i386/usr/src/usr.bin/objcopy'
.MAKE='make'
.OBJDIR='/usr/local/release-builds/i386/tmp/obj/usr/local/release-builds/i386/usr/src/amd64.amd64/usr.bin/objcopy'
.TARGETS='all'
DESTDIR='/usr/local/release-builds/i386/tmp/obj/usr/local/release-builds/i386/usr/src/amd64.amd64/tmp'
LD_LIBRARY_PATH=''
MACHINE='amd64'
MACHINE_ARCH='amd64'
MAKEOBJDIRPREFIX=''
MAKESYSPATH='/usr/local/release-builds/i386/usr/src/share/mk'

	imb