r40678 added this copy workaround.
Bug #4342 is now
Its version 0.6 comment reads:
I verified on Windows that at least QEMU 0.9.1 does lock the Iso file, so 7-Zip fails.
But, if the Iso file is set to beforehand, QEMU does not lock it, so 7-Zip can unpack it as is.
In this case, the copy workaround is counterproductive: uselessly copying, i.e., a 134 MiB "bootcdregtest".
It may be possible, for example, to add an additional check, using maybe Linux stat() and Windows GetFileAttributes()...