improve fakechroot LD_LIBRARY_PATH

- use /etc/ld.so.conf from the chroot instead of the host
 - parse /etc/ld.so.conf instead of blindly accessing /etc/ld.so.conf.d
 - add libraries from the chroot instead of the host

mmdebstrap

@@ -2697,17 +2697,6 @@ sub run_prepare {
             $ENV{FAKECHROOT_AF_UNIX_PATH} = "/tmp";
         }
         {
-            my @ldsoconf = ('/etc/ld.so.conf');
-            opendir(my $dh, '/etc/ld.so.conf.d')
-              or error "Can't opendir(/etc/ld.so.conf.d): $!";
-            while (my $entry = readdir $dh) {
-                # skip the "." and ".." entries
-                next if $entry eq ".";
-                next if $entry eq "..";
-                next if $entry !~ /\.conf$/;
-                push @ldsoconf, "/etc/ld.so.conf.d/$entry";
-            }
-            closedir($dh);
             my @ldlibpath = ();
             if (defined $ENV{LD_LIBRARY_PATH}
                 && $ENV{LD_LIBRARY_PATH} ne "") {
@@ -2715,15 +2704,34 @@ sub run_prepare {
             }
             # FIXME: workaround allowing installation of systemd should
             # live in fakechroot, see #917920
-            push @ldlibpath, "/lib/systemd";
-            foreach my $fname (@ldsoconf) {
-                open my $fh, "<", $fname
-                  or error "cannot open $fname for reading: $!";
-                while (my $line = <$fh>) {
-                    next if $line !~ /^\//;
-                    push @ldlibpath, $line;
+            push @ldlibpath, "$options->{root}/lib/systemd";
+            my $parse_ld_so_conf;
+            $parse_ld_so_conf = sub {
+                foreach my $conf (@_) {
+                    next if !-r $conf;
+                    open my $fh, '<', "$conf" or error "can't read $conf: $!";
+                    while (my $line = <$fh>) {
+                        chomp $line;
+                        if ($line eq "") {
+                            next;
+                        }
+                        if ($line =~ /^#/) {
+                            next;
+                        }
+                        if ($line =~ /include (.*)/) {
+                            $parse_ld_so_conf->(glob("$options->{root}/$1"));
+                            next;
+                        }
+                        if (!-d "$options->{root}/$line") {
+                            next;
+                        }
+                        push @ldlibpath, "$options->{root}/$line";
+                    }
+                    close $fh;
                 }
-                close $fh;
+            };
+            if (-e "$options->{root}/etc/ld.so.conf") {
+                $parse_ld_so_conf->("$options->{root}/etc/ld.so.conf");
             }
             ## no critic (Variables::RequireLocalizedPunctuationVars)
             $ENV{LD_LIBRARY_PATH} = join ':', @ldlibpath;
@@ -6483,9 +6491,8 @@ fakeroot.env> and use C<fakeroot.env> later when entering the chroot with
 C<fakechroot fakeroot -i fakeroot.env chroot ...>. This mode will not work if
 maintainer scripts are unable to handle C<LD_PRELOAD> correctly like the
 package B<initramfs-tools> until version 0.132. This mode will also not work
-with a different libc inside the chroot than on the outside. Since ldconfig
-cannot run under fakechroot, the final system will not contain
-F</etc/ld.so.cache>. See the section B<LIMITATIONS> in B<fakechroot(1)>.
+with a different libc inside the chroot than on the outside. See the section
+B<LIMITATIONS> in B<fakechroot(1)>.
 
 =item B<proot>