llvm-build: Fill in some details w.r.t. component's parents.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@143624 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/utils/llvm-build/llvmbuild/componentinfo.py b/utils/llvm-build/llvmbuild/componentinfo.py
index 22ce0b4..30ec23b 100644
--- a/utils/llvm-build/llvmbuild/componentinfo.py
+++ b/utils/llvm-build/llvmbuild/componentinfo.py
@@ -37,6 +37,15 @@
         # under.
         self.parent = parent
 
+        # The parent instance, once loaded.
+        self.parent_instance = None
+        self.children = []
+
+    def set_parent_instance(self, parent):
+        assert parent.name == self.parent, "Unexpected parent!"
+        self.parent_instance = parent
+        self.parent_instance.children.append(self)
+
     def get_component_references(self):
         """get_component_references() -> iter