Bump unwinder private data size for AArch64 Windows

This fixes unwinding on `aarch64-*-windows-gnu*`.

Author: mati865

library/unwind/src/libunwind.rs

@@ -36,9 +36,12 @@ pub const unwinder_private_data_size: usize = 20;
 #[cfg(all(target_arch = "arm", any(target_os = "ios", target_os = "watchos")))]
 pub const unwinder_private_data_size: usize = 5;
 
-#[cfg(all(target_arch = "aarch64", target_pointer_width = "64"))]
+#[cfg(all(target_arch = "aarch64", target_pointer_width = "64", not(target_os = "windows")))]
 pub const unwinder_private_data_size: usize = 2;
 
+#[cfg(all(target_arch = "aarch64", target_pointer_width = "64", target_os = "windows"))]
+pub const unwinder_private_data_size: usize = 6;
+
 #[cfg(all(target_arch = "aarch64", target_pointer_width = "32"))]
 pub const unwinder_private_data_size: usize = 5;