save file block allocations in target_files

make_ext4fs can now output a file listing the blocks used for each
file in the image.  Request this file and save it in the target_files;
it will be used for future improvements to block OTAs.

Bug: 16984795
Change-Id: Id1e60465e3b5a9d126a7934b4d089cf34d8fec44
diff --git a/tools/releasetools/build_image.py b/tools/releasetools/build_image.py
index 712e0cd..5ae8d3c 100755
--- a/tools/releasetools/build_image.py
+++ b/tools/releasetools/build_image.py
@@ -209,7 +209,8 @@
 
 def BuildImage(in_dir, prop_dict, out_file,
                fs_config=None,
-               fc_config=None):
+               fc_config=None,
+               block_list=None):
   """Build an image to out_file from in_dir with property prop_dict.
 
   Args:
@@ -252,6 +253,8 @@
       build_command.extend(["-T", str(prop_dict["timestamp"])])
     if fs_config is not None:
       build_command.extend(["-C", fs_config])
+    if block_list is not None:
+      build_command.extend(["-B", block_list])
     if fc_config is not None:
       build_command.append(fc_config)
     elif "selinux_fc" in prop_dict: