libunwind: unwinder_private_data_size for sparc64

Author: jakllsch

src/libunwind/libunwind.rs

@@ -65,6 +65,9 @@ pub const unwinder_private_data_size: usize = 2;
 #[cfg(target_arch = "s390x")]
 pub const unwinder_private_data_size: usize = 2;
 
+#[cfg(target_arch = "sparc64")]
+pub const unwinder_private_data_size: usize = 2;
+
 #[cfg(target_os = "emscripten")]
 pub const unwinder_private_data_size: usize = 20;