The problem is it unconditionally appends the output of GCC's -print-multi-os-directory flag to the install location, whereas when installing in $SAGE_LOCAL we just always want $SAGE_LOCAL/lib.

This is already fixed upstream, so we just need to include that patch.

CC: @strogdon @fchapoton @jdemeyer

Component: packages: standard

Author: Erik Bray

Branch/Commit: bfa7c90

Reviewer: Jeroen Demeyer

Issue created by migration from https://trac.sagemath.org/ticket/27109