systemd: don't taint on unmerged /usr

Discussion: https://github.com/systemd/systemd/issues/24191#issuecomment-1209350080

pkgs/os-specific/linux/systemd/0018-core-don-t-taint-on-unmerged-usr.patch

@@ -0,0 +1,33 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: oxalica <oxalicc@pm.me>
+Date: Tue, 4 Oct 2022 09:18:07 +0800
+Subject: [PATCH] core: don't taint on unmerged /usr
+
+NixOS has very different approach towards /bin and /sbin - they don't
+really exist (except for /bin/sh and /usr/bin/env, because these are used
+heavily in shebangs around the world). The concept of merged or unmerged
+usr doesn't really apply here at all, it's neither of the two.
+Users don't execute things from /bin or /sbin, there's nothing else in
+there. In all cases, systemd doesn't look things up from /usr/bin or /bin,
+so showing the taint isn't really helpful.
+
+See also: https://github.com/systemd/systemd/issues/24191
+---
+ src/core/manager.c | 4 ----
+ 1 file changed, 4 deletions(-)
+
+diff --git a/src/core/manager.c b/src/core/manager.c
+index 33ded94a7c..8847479799 100644
+--- a/src/core/manager.c
++++ b/src/core/manager.c
+@@ -4488,10 +4488,6 @@ char* manager_taint_string(const Manager *m) {
+         if (m->taint_usr)
+                 stage[n++] = "split-usr";
+ 
+-        _cleanup_free_ char *usrbin = NULL;
+-        if (readlink_malloc("/bin", &usrbin) < 0 || !PATH_IN_SET(usrbin, "usr/bin", "/usr/bin"))
+-                stage[n++] = "unmerged-usr";
+-
+         if (access("/proc/cgroups", F_OK) < 0)
+                 stage[n++] = "cgroups-missing";
+ 

pkgs/os-specific/linux/systemd/default.nix

@@ -163,6 +163,7 @@ stdenv.mkDerivation {
     ./0015-path-util.h-add-placeholder-for-DEFAULT_PATH_NORMAL.patch
     ./0016-pkg-config-derive-prefix-from-prefix.patch
     ./0017-inherit-systemd-environment-when-calling-generators.patch
+    ./0018-core-don-t-taint-on-unmerged-usr.patch
   ] ++ lib.optional stdenv.hostPlatform.isMusl (
     let
       oe-core = fetchzip {