Revise partition size for system_other.img

system_other may be dynamic partition.
Do not fix its partition size as system's.

Bug: 220258352
Change-Id: Iacd14769ec14f43e3871d3c50a6627e6471284b1
diff --git a/tools/releasetools/build_image.py b/tools/releasetools/build_image.py
index 4b5846d..dbd2c6f 100755
--- a/tools/releasetools/build_image.py
+++ b/tools/releasetools/build_image.py
@@ -705,7 +705,7 @@
       if mount_point not in allowed_partitions:
           continue
 
-    if mount_point == "system_other":
+    if (mount_point == "system_other") and (dest_prop != "partition_size"):
       # Propagate system properties to system_other. They'll get overridden
       # after as needed.
       copy_prop(src_prop.format("system"), dest_prop)