Adapt backup variable to upstream changes
polkit moved their vendored PAM config from /etc to /usr/lib: https://github.com/polkit-org/polkit/commit/22193ca2cc0f4e023d331cc1391f55143ef9cade
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polkit moved their vendored PAM config from /etc to /usr/lib: https://github.com/polkit-org/polkit/commit/22193ca2cc0f4e023d331cc1391f55143ef9cade