feat: start of archive generation for new manager

libarchive/src/write/builder.rs

@@ -11,6 +11,8 @@ pub struct Builder {
     consumed: bool,
 }
 
+unsafe impl Send for Builder {}
+
 impl Builder {
     pub fn new() -> Self {
         Builder::default()

libarchive/src/write/file.rs

@@ -13,6 +13,8 @@ pub struct FileWriter {
     closed: bool,
 }
 
+unsafe impl Send for FileWriter {}
+
 impl Handle for FileWriter {
     unsafe fn handle(&self) -> *const ffi::Struct_archive {
         self.handle as *const _

libarchive/src/write/mod.rs

@@ -9,6 +9,8 @@ pub struct WriteEntry {
     entry: *mut ffi::Struct_archive_entry,
 }
 
+unsafe impl Send for WriteEntry {}
+
 impl WriteEntry {
     pub fn new() -> Self {
         let entry = unsafe { ffi::archive_entry_new() };