fix build failure caused by imprecise libc version specification
fix build failure caused by imprecise libc version specification

- more precisely describe permissable libc versions

.# [why]

- libc >= v0.2.15 is needed for utmp support.
- libc <= v0.2.66 is required to avoid build errors for MinSRV == 1.31.0.

Intermittant build failures were being caused by `cargo` using early libc versions.

uutils/coreutils,uutils/coreutils,uutils/coreutils