sccache-overlay and different major os versions

Hello, am asking this here because I guess most of you will be familiar with
building in poudriere.

Is it expected that using sccache-overlay will work when the host is running
current but the builder is for example a 14.1-p6 poudriere jail?

errors like

[00:00:03] ==> Starting sccache
[00:00:03] ld-elf.so.1: Shared object "libsys.so.7" not found, required by
"libthr.so.3"
[00:00:03] ld-elf.so.1: Shared object "libsys.so.7" not found, required by
"libthr.so.3"
[00:00:03] *** Error code 1
[00:00:03] 
[00:00:03] Stop.
[00:00:03] make[1]: stopped in /usr/ports/ports-mgmt/pkg

The error doesn't happen if the poudriere host and the poudriere 
jail are both at -current. The workaround on my host has been not to use -O
sccache with poudriere for builders of a less major version than the host.

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