llvm-build: Add sketchy support for preserving comments when using
--write-llvmbuild.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@146434 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/utils/llvm-build/llvmbuild/componentinfo.py b/utils/llvm-build/llvmbuild/componentinfo.py
index 079102f..e9ef973 100644
--- a/utils/llvm-build/llvmbuild/componentinfo.py
+++ b/utils/llvm-build/llvmbuild/componentinfo.py
@@ -42,6 +42,9 @@
         self.parent_instance = None
         self.children = []
 
+        # The original source path.
+        self._source_path = None
+
     def set_parent_instance(self, parent):
         assert parent.name == self.parent, "Unexpected parent!"
         self.parent_instance = parent
@@ -407,4 +410,5 @@
             fatal("unable to load component %r in %r: %s" % (
                     section, path, e.message))
 
+        info._source_path = path
         yield info