[builder] don't exit if no args are given, allowing creating up-to-dated container with all set-up for compilation also if no args are given. adding --help

builder

@@ -28,21 +28,20 @@ my $enman_repositories   = $ENV{ENMAN_REPOSITORIES};
 my $prune_virtuals       = $ENV{PRUNE_VIRTUALS} // 0;
 my $repository_name      = $ENV{REPOSITORY_NAME};
 my $enman_add_self       = $ENV{ENMAN_ADD_SELF} // 1;
+my $build_injected_args  = $ENV{BUILD_INJECTED_ARGS};
 
 my $make_conf = $ENV{MAKE_CONF};
 
 my @overlays;
-
+my $help=0;
 GetOptions(
     'layman|overlay:s{,}' => \@overlays,
     'equo|install:s{,}'   => \@equo_install,
-    'equorm|remove:s{,}'  => \@equo_remove
+    'equorm|remove:s{,}'  => \@equo_remove,
+    'help|?' => \$help
 );
 
-if ( @ARGV == 0 ) {
-    help();
-    die();
-}
+help() if $help;
 
 $ENV{LC_ALL} = "en_US.UTF-8";    #here be dragons
 
@@ -161,6 +160,7 @@ sub help {
 "You can supply multiple overlays as well: $0 plasma-meta --layman kde plab",
       "The documentation is available at https://github.com/Sabayon/devkit",
       "";
+    exit 0;
 }
 
 say "****************************************************";
@@ -330,6 +330,12 @@ else {
 
 my $return = $rt >> 8;
 
+# best effort -B
+if ($build_injected_args) {
+    system("emerge $emerge_defaults_args -j $jobs -B $_")
+      for ( split( / /, $build_injected_args ) );
+}
+
 if ($preserved_rebuild) {
 
     system("emerge -j $jobs --buildpkg \@preserved-rebuild");