Add size to the initfs header

src/types.rs

@@ -72,6 +72,7 @@ pub struct Header {
     pub creation_time: Timespec,
     pub inode_count: U16,
     pub bootstrap_entry: U64,
+    pub initfs_size: U64,
 }
 
 const _: () = {

tools/src/archive_common.rs

@@ -487,6 +487,7 @@ pub fn archive(
             inode_count: state.inode_count.into(),
             inode_table_offset,
             bootstrap_entry: bootstrap_entry.into(),
+            initfs_size: state.file.metadata().context("failed to get initfs size")?.len().into(),
         };
         write_all_at(&*state.file, &header_bytes, header_offset, "writing header")
             .context("failed to write header")?;