Add a new flag "--disable_fec_computation" for OTA generation

We have added the flag to disable on device fec computation in
brillo_update_payload. Exposed it in ota_from_target_files as well.

Bug: 139723500
Test: generate an incremental package with the new flag
Change-Id: I683e3ec7791963a3c7e141ecb4e5a3fb53fe2108

tools/releasetools/ota_from_target_files.py

@@ -139,6 +139,9 @@ Non-A/B OTA specific options
 
 A/B OTA specific options
 
+  --disable_fec_computation
+      Disable the on device FEC data computation for incremental updates.
+
   --include_secondary
       Additionally include the payload for secondary slot images (default:
       False). Only meaningful when generating A/B OTAs.
@@ -235,6 +238,7 @@ OPTIONS.skip_postinstall = False
 OPTIONS.retrofit_dynamic_partitions = False
 OPTIONS.skip_compatibility_check = False
 OPTIONS.output_metadata_path = None
+OPTIONS.disable_fec_computation = False
 
 
 METADATA_NAME = 'META-INF/com/android/metadata'
@@ -571,6 +575,8 @@ class Payload(object):
            "--target_image", target_file]
     if source_file is not None:
       cmd.extend(["--source_image", source_file])
+      if OPTIONS.disable_fec_computation:
+        cmd.extend(["--disable_fec_computation", "true"])
     cmd.extend(additional_args)
     self._Run(cmd)
 
@@ -2225,6 +2231,8 @@ def main(argv):
       OPTIONS.skip_compatibility_check = True
     elif o == "--output_metadata_path":
       OPTIONS.output_metadata_path = a
+    elif o == "--disable_fec_computation":
+      OPTIONS.disable_fec_computation = True
     else:
       return False
     return True
@@ -2259,6 +2267,7 @@ def main(argv):
                                  "retrofit_dynamic_partitions",
                                  "skip_compatibility_check",
                                  "output_metadata_path=",
+                                 "disable_fec_computation",
                              ], extra_option_handler=option_handler)
 
   if len(args) != 2: