Look for non-existent files listed in avb_vbmeta_args.

"--include_descriptors_from_image" with an image file whose path points
to source tree, add_img_to_target_files.py or sign_target_files_apks.py
may fail to find the file. Because these scripts may run without a
source tree, by taking target_files.zip as the only input.

This CL scans additional locations in the input target_files.zip to find
those missing files in avb_vbmeta_args. As long as the files are included
in the target_files.zip, they get a second chance to be found.

Bug: 63910867
Test: As follows:
 1. Setup BOARD_AVB_MAKE_VBMETA_IMAGE_ARGS with a local file path;
 2. Remove the local file;
 3. sign_target_files_apks.py fails without this CL;
 4. sign_target_files_apks.py works.
Change-Id: I3c58f80a5535db02b74cfe40d0c0beff72587cf8
diff --git a/tools/releasetools/add_img_to_target_files.py b/tools/releasetools/add_img_to_target_files.py
index 4a85496..cf78d5e 100755
--- a/tools/releasetools/add_img_to_target_files.py
+++ b/tools/releasetools/add_img_to_target_files.py
@@ -377,7 +377,27 @@
   args = OPTIONS.info_dict.get("avb_vbmeta_args")
   if args and args.strip():
-    cmd.extend(shlex.split(args))
+    split_args = shlex.split(args)
+    for index, arg in enumerate(split_args[:-1]):
+      # Sanity check that the image file exists. Some images might be defined
+      # as a path relative to source tree, which may not be available at the
+      # same location when running this script (we have the input target_files
+      # zip only). For such cases, we additionally scan other locations (e.g.
+      # IMAGES/, RADIO/, etc) before bailing out.
+      if arg == '--include_descriptors_from_image':
+        image_path = split_args[index + 1]
+        if os.path.exists(image_path):
+          continue
+        found = False
+        for dir in ['IMAGES', 'RADIO', 'VENDOR_IMAGES', 'PREBUILT_IMAGES']:
+          alt_path = os.path.join(
+              OPTIONS.input_tmp, dir, os.path.basename(image_path))
+          if os.path.exists(alt_path):
+            split_args[index + 1] = alt_path
+            found = True
+            break
+        assert found, 'failed to find %s' % (image_path,)
+    cmd.extend(split_args)
   p = common.Run(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE)