[gnome-builder] vala: steal string from GString

[Christian Hergert <chergert src gnome org>]

commit 800bfee685f4d5a689f68e908f750695de35b07d
Author: Christian Hergert <christian hergert me>
Date:   Thu Oct 1 16:54:28 2015 -0700

    vala: steal string from GString

 plugins/vala-pack/ide-vala-completion-item.vala |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/plugins/vala-pack/ide-vala-completion-item.vala b/plugins/vala-pack/ide-vala-completion-item.vala
index 3b78c19..56f2731 100644
--- a/plugins/vala-pack/ide-vala-completion-item.vala
+++ b/plugins/vala-pack/ide-vala-completion-item.vala
@@ -133,7 +133,8 @@ namespace Ide
                                str.append (this.symbol.name);
                        }
 
-                       this.label = str.str;
+                       /* Steal the string instead of strdup */
+                       this.label = (owned)str.str;
                }
 
                public string get_markup () {