nix/doc/manual/rl-next/homeless-shelter-to-proc.md

synopsis	issues	prs
On linux, set $HOME=/proc/homeless-shelter instead of /homeless-shelter	8313 11295	11300

When building, $HOME is set to a non-existing directory. Previously it was always set to /homeless-shelter. Before a build, Nix verifies that it doesn't exist. In some scenarios (specifically when using the Linux sandbox with a single-user installation), it is possible to create the /homeless-shelter directory, and some tools will create it, resulting in a build error.

Now, on Linux, $HOME is set to /proc/homeless-shelter. This directory can never be created, since /proc is a virtual filesystem. This resolves the issue.