c9s+ppc64le: rm: write error: Bad file descriptor

We're seeing this only on pp64le

>>>> Executing `postprocess` inline script '11' <<<<
+ rm -vrf /usr/lib/ostree-boot/loader 
rm: write error: Bad file descriptor

Tracing some of the code in coreutils...I think what's going on is rm is failing to write to std{out,err}. Ref e.g. https://github.com/coreutils/coreutils/blob/083f89528ed77d91fd780c5fc81652aef319934b/src/comm.c#L168

And the fact that this is only C9S, and also apparently not something seen elsewhere to me makes it likely that this is related to https://github.com/coreos/rpm-ostree/pull/5388 - i.e. it's either fixed by that (if we have that PR in c10s) or caused by that (if that patch is only in c9s).