As stated in D41023, on my mac `xargs -n2147483647 < usr.bin/xargs/tests/regress.in`, works fine.
However both, on my testing FreeBSD VM, and on CirrusCI (https://cirrus-ci.com/task/4770881373732864), it fails -- maybe I need to update the VMs.
At any rate, this patch is needed in order to run the tests.