Merge pull request #11366 from Mic92/homeless-shelter

Revert: Make $HOME=/proc/homeless-shelter instead of /homeless-shelter

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

@@ -1,9 +0,0 @@
----
-synopsis: On linux, set $HOME=/proc/homeless-shelter instead of /homeless-shelter
-issues: [8313, 11295]
-prs: [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.

doc/manual/src/language/derivations.md

@@ -264,8 +264,7 @@ The [`builder`](#attr-builder) is executed as follows:
   - `PATH` is set to `/path-not-set` to prevent shells from
     initialising it to their built-in default value.
 
-  - `HOME` is set to `/proc/homeless-shelter` on Linux and `/homeless-shelter`
-    on OSX, to prevent programs from
+  - `HOME` is set to `/homeless-shelter` to prevent programs from
     using `/etc/passwd` or the like to find the user's home
     directory, which could cause impurity. Usually, when `HOME` is
     set, it is used as the location of the home directory, even if

src/libstore/unix/build/local-derivation-goal.cc

@@ -102,14 +102,7 @@ void handleDiffHook(
     }
 }
 
-// We want $HOME to be un-creatable in the sandbox. On Linux,
-// you can't create anything inside /proc since it's a virtual filesystem.
-// On Darwin it seems that `/homeless-shelter` is good enough.
-#if __linux__
-const Path LocalDerivationGoal::homeDir = "/proc/homeless-shelter";
-#else
 const Path LocalDerivationGoal::homeDir = "/homeless-shelter";
-#endif
 
 
 LocalDerivationGoal::~LocalDerivationGoal()