documentation: Recommend GNU stow to people who want to install to /usr/local #21536
Description
#21479 allows to set --prefix, but of course we can't write to /usr/local because we aren't root at 'make' time. (See also #21495.)
So, for people who really want all software in /usr/local, we could just point them to https://www.gnu.org/software/stow/ in the documentation.
Haven't used that in 10 years, but looks like it is still maintained.
Depends on #21479
Component: documentation
Issue created by migration from https://trac.sagemath.org/ticket/21536