Rollup merge of rust-lang#104464 - mati865:reduce-eh-overallocation-amd64, r=thomcc

Reduce exceptions overallocation on non Windows x86_64

Addressing rust-lang#103894 (comment)

Author: Dylan-DPC

library/unwind/src/libunwind.rs

@@ -27,7 +27,10 @@ pub type _Unwind_Trace_Fn =
 #[cfg(target_arch = "x86")]
 pub const unwinder_private_data_size: usize = 5;
 
-#[cfg(target_arch = "x86_64")]
+#[cfg(all(target_arch = "x86_64", not(target_os = "windows")))]
+pub const unwinder_private_data_size: usize = 2;
+
+#[cfg(all(target_arch = "x86_64", target_os = "windows"))]
 pub const unwinder_private_data_size: usize = 6;
 
 #[cfg(all(target_arch = "arm", not(any(target_os = "ios", target_os = "watchos"))))]