Fix non-AB ota generation for directories

Test: ota_from_target_files -v --block yukawa-target_files-10097950.zip
test.zip

Change-Id: I4291010d66cc28bdb6b6b334cdbed06daf3de837
diff --git a/tools/releasetools/ota_from_target_files.py b/tools/releasetools/ota_from_target_files.py
index 1a4a895..04ef5ef 100755
--- a/tools/releasetools/ota_from_target_files.py
+++ b/tools/releasetools/ota_from_target_files.py
@@ -273,7 +273,6 @@
                        PayloadGenerator, SECURITY_PATCH_LEVEL_PROP_NAME, ExtractTargetFiles, CopyTargetFilesDir)
 from common import DoesInputFileContain, IsSparseImage
 import target_files_diff
-from check_target_files_vintf import CheckVintfIfTrebleEnabled
 from non_ab_ota import GenerateNonAbOtaPackage
 from payload_signer import PayloadSigner
 
@@ -954,6 +953,7 @@
   target_info.info_dict['ab_partitions'] = common.ReadFromInputFile(target_file,
                                                                     AB_PARTITIONS).strip().split("\n")
 
+  from check_target_files_vintf import CheckVintfIfTrebleEnabled
   CheckVintfIfTrebleEnabled(target_file, target_info)
 
   # Metadata to comply with Android OTA package format.