Create a partial implementation of $PRODUCT_OUT/misc_info.txt

This file is packaged into META/target_files.zip. It is also an implicit
input for `add_img_to_target_files` invocation, which creates additional
metadata files for target_files.zip like apex_info.pb, care_map.pb and
vbmeta_digest.txt

This CL implements the minimum fields necessary to run
`add_img_to_target_files`.

Bug: 399788119
Test: Built target_files.zip locally.
Test: Verified META/misc_info.txt exists, but is not identical to make
Change-Id: I52b9c9ff7b33e74d79b9321aa94312397a830693
diff --git a/filesystem/filesystem.go b/filesystem/filesystem.go
index fc480e6..35fdd00 100644
--- a/filesystem/filesystem.go
+++ b/filesystem/filesystem.go
@@ -436,6 +436,8 @@
 	FilesystemConfig android.Path
 
 	Owners []InstalledModuleInfo
+
+	UseAvb bool
 }
 
 // FullInstallPathInfo contains information about the "full install" paths of all the files
@@ -680,6 +682,7 @@
 		SelinuxFc:          f.selinuxFc,
 		FilesystemConfig:   f.generateFilesystemConfig(ctx, rootDir, rebasedDir),
 		Owners:             f.gatherOwners(specs),
+		UseAvb:             proptools.Bool(f.properties.Use_avb),
 	}
 
 	android.SetProvider(ctx, FilesystemProvider, fsInfo)