I get:

--8<---------------cut here---------------start------------->8---
$ ./pre-inst-env guix system build gnu/system/examples/lightweight-desktop.tmpl
substitute: updating list of substitutes from 'https://mirror.hydra.gnu.org'... 100.0%
substitute: updating list of substitutes from 'https://hydra.gnu.org'... 100.0%

[...]

/gnu/store/rx31x0m8fk5aknwf754in9yxl7vcq8ls-system
$ grep pam_limit /gnu/store/rx31x0m8fk5aknwf754in9yxl7vcq8ls-system/etc/pam.d/*
/gnu/store/rx31x0m8fk5aknwf754in9yxl7vcq8ls-system/etc/pam.d/login:session required pam_limits.so conf=/etc/security/limits.conf
/gnu/store/rx31x0m8fk5aknwf754in9yxl7vcq8ls-system/etc/pam.d/slim:session required pam_limits.so conf=/etc/security/limits.conf
/gnu/store/rx31x0m8fk5aknwf754in9yxl7vcq8ls-system/etc/pam.d/su:session required pam_limits.so conf=/etc/security/limits.conf
--8<---------------cut here---------------end--------------->8---

Could you try it?

Thanks,
Ludo’.