Strange failure in stage when COPYTREE_SHARE is used

Good evening!

For over a month now builds of lang/mecrisp-stellaris and
other ports seem to fail on the build cluster when build for
armv6/armv7 under QEMU during staging, see e.g. here:

https://lists.freebsd.org/archives/freebsd-pkg-fallout/2021-June/018350.html

There is no error message, COPYTREE_SHARE just fails.  Any
idea what could cause this?  I was unable to reproduce this
issue on my native armv7 system or with QEMU on my amd64
system.

Yours,
Robert Clausecker

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