devkit/builder: replace layman with eselect-repository

- Setup: eselect-repository add + emaint sync instead of layman -f -a
- Remove: drop layman mkdir/make.conf/layman-updater setup block
- Sync: emerge --sync instead of layman -S

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

builder

@@ -578,11 +578,7 @@ if ( $remote_portdir ne "" ) {
     _system("git clone $remote_portdir /usr/portage");
 }
 
-_system("mkdir /var/lib/layman") if ( !-d "/var/lib/layman" );
-_system("touch /var/lib/layman/make.conf && layman-updater -R")
-    if ( !-e "/var/lib/layman/make.conf" );
-
-_system("echo 'y' | layman -f -a $_") for @overlays;
+_system("eselect repository add $_ git https://github.com/gentoo-mirror/$_.git && emaint sync -r $_") for @overlays;
 
 my $reponame = "LocalOverlay";
 
@@ -621,7 +617,7 @@ if ( $remote_overlay and $remote_overlay ne "" ) {
 if ( $remove_layman_overlay and $remove_layman_overlay ne "" ) {
     say "===== Removing overlays: $remove_layman_overlay =====";
 
-    _system("layman -d $_") for ( split( / /, $remove_layman_overlay ) );
+    _system("eselect repository disable $_ && emaint sync -r $_") for ( split( / /, $remove_layman_overlay ) );
 }
 if ( $remove_remote_overlay and $remove_remote_overlay ne "" ) {
     say "===== Removing overlays: $remove_remote_overlay =====";
@@ -635,7 +631,7 @@ portage_perms('/usr/portage');
 unless ( $skip_portage_sync == 1 ) {
 
     # sync portage and overlays
-    _system("layman -S");
+    _system("emerge --sync --quiet");
     if ( $portage_git_url ne "" and $portage_git_branch ne "" ) {
       fetch_portage_from_git( $portage_git_url, $portage_git_service,
         $portage_git_branch );