This resolves the issue reported at https://groups.google.com/d/msg/sage-devel/w6Os2s6_eGk/SyFxT7cJBgAJ that the primecount SPKG will try to install libraries to lib64 on some platforms.

Depends on #27484

CC: @videlec @dimpase

Component: packages: optional

Author: Erik Bray

Branch: b244e65

Reviewer: Dima Pasechnik

Issue created by migration from https://trac.sagemath.org/ticket/27485