parallelize add_partition_calls

it made total time equal to the longest image build

1m10s->30s in local build

Bug: 281960217
Test: m dist
Change-Id: I13d4f45d9b46b39292a014e3b4e1913365d89b7a
diff --git a/tools/releasetools/add_img_to_target_files.py b/tools/releasetools/add_img_to_target_files.py
index ac3271b..934b73f 100644
--- a/tools/releasetools/add_img_to_target_files.py
+++ b/tools/releasetools/add_img_to_target_files.py
@@ -65,7 +65,7 @@
 import ota_metadata_pb2
 import rangelib
 import sparse_img
-
+from concurrent.futures import ThreadPoolExecutor
 from apex_utils import GetApexInfoFromTargetFiles
 from common import ZipDelete, PARTITIONS_WITH_CARE_MAP, ExternalError, RunAndCheckOutput, IsSparseImage, MakeTempFile, ZipWrite
 
@@ -1083,8 +1083,10 @@
       ("system_dlkm", has_system_dlkm, AddSystemDlkm, []),
       ("system_other", has_system_other, AddSystemOther, []),
   )
-  for call in add_partition_calls:
-    add_partition(*call)
+
+  with ThreadPoolExecutor(max_workers=len(add_partition_calls)) as executor:
+    for future in [executor.submit(add_partition, *call) for call in add_partition_calls]:
+      future.result()
 
   AddApexInfo(output_zip)