Revert "Merge pull request #54980 from danbst/etc-relative" (#56507)

This reverts commit 0b91fa43e4, reversing
changes made to 183919a0c0.

nixos/modules/system/etc/setup-etc.pl

@@ -4,7 +4,6 @@ use File::Copy;
 use File::Path;
 use File::Basename;
 use File::Slurp;
-use File::Spec;
 
 my $etc = $ARGV[0] or die;
 my $static = "/etc/static";
@@ -18,20 +17,6 @@ sub atomicSymlink {
     return 1;
 }
 
-# Create relative symlinks, so that the links can be followed if
-# the NixOS installation is not mounted as filesystem root.
-# Absolute symlinks violate the os-release format
-# at https://www.freedesktop.org/software/systemd/man/os-release.html
-# and break e.g. systemd-nspawn and os-prober.
-sub atomicRelativeSymlink {
-    my ($source, $target) = @_;
-    my $tmp = "$target.tmp";
-    unlink $tmp;
-    my $rel = File::Spec->abs2rel($source, dirname $target);
-    symlink $rel, $tmp or return 0;
-    rename $tmp, $target or return 0;
-    return 1;
-}
 
 # Atomically update /etc/static to point at the etc files of the
 # current configuration.
@@ -118,7 +103,7 @@ sub link {
     if (-e "$_.mode") {
         my $mode = read_file("$_.mode"); chomp $mode;
         if ($mode eq "direct-symlink") {
-            atomicRelativeSymlink readlink("$static/$fn"), $target or warn;
+            atomicSymlink readlink("$static/$fn"), $target or warn;
         } else {
             my $uid = read_file("$_.uid"); chomp $uid;
             my $gid = read_file("$_.gid"); chomp $gid;
@@ -132,7 +117,7 @@ sub link {
         push @copied, $fn;
         print CLEAN "$fn\n";
     } elsif (-l "$_") {
-        atomicRelativeSymlink "$static/$fn", $target or warn;
+        atomicSymlink "$static/$fn", $target or warn;
     }
 }