Mark __rgl_oom and __rd_oom as "C-unwind"

Author: Amanieu

library/alloc/src/alloc.rs

@@ -396,13 +396,13 @@ pub mod __alloc_error_handler {
 
     // if there is no `#[alloc_error_handler]`
     #[rustc_std_internal_symbol]
-    pub unsafe extern "C" fn __rdl_oom(size: usize, _align: usize) -> ! {
+    pub unsafe extern "C-unwind" fn __rdl_oom(size: usize, _align: usize) -> ! {
         panic!("memory allocation of {} bytes failed", size)
     }
 
     // if there is an `#[alloc_error_handler]`
     #[rustc_std_internal_symbol]
-    pub unsafe extern "C" fn __rg_oom(size: usize, align: usize) -> ! {
+    pub unsafe extern "C-unwind" fn __rg_oom(size: usize, align: usize) -> ! {
         let layout = unsafe { Layout::from_size_align_unchecked(size, align) };
         extern "Rust" {
             #[lang = "oom"]

library/alloc/src/lib.rs

@@ -163,6 +163,7 @@
 #![cfg_attr(test, feature(test))]
 #![feature(unboxed_closures)]
 #![feature(unsized_fn_params)]
+#![feature(c_unwind)]
 //
 // Rustdoc features:
 #![feature(doc_cfg)]