Revert "libutil: add makeTempSiblingPath helper"

Revert submission 3850

Reason for revert: caused multiple regressions noticed in https://git.lix.systems/lix-project/lix/issues/975 and https://git.lix.systems/lix-project/lix/issues/966 (suspected).

Root cause analysis has not been done yet and this breaks Lix on Darwin on HEAD.

Reverted changes: /q/submissionid:3850

Change-Id: Ifc8ccc212ec73f51958b20c9419c81d723f87b0d

lix/libutil/file-system.cc

@@ -693,11 +693,6 @@ Path makeTempPath(const Path & root, const Path & suffix)
     return fmt("%1%%2%-%3%-%4%", root, suffix, getpid(), counter.fetch_add(1, std::memory_order_relaxed));
 }
 
-Path makeTempSiblingPath(const Path & path)
-{
-    return makeTempPath(fs::path(path).remove_filename());
-}
-
 void createSymlink(const Path & target, const Path & link)
 {
     if (symlink(target.c_str(), link.c_str()))

lix/libutil/file-system.hh

@@ -318,11 +318,6 @@ Path createTempSubdir(const Path & parent, const Path & prefix = "nix",
  */
 Path makeTempPath(const Path & root, const Path & suffix = ".tmp");
 
-/**
- * Return temporary path in the same directory as a given path.
- */
-Path makeTempSiblingPath(const Path & root);
-
 /**
  * Used in various places.
  */