Rollup merge of #30801 - Amanieu:oom_print, r=alexcrichton

This adds the ability to override the default OOM behavior by setting a handler function. This is used by libstd to print a message when running out of memory instead of crashing with an obscure "illegal hardware instruction" error (at least on Linux).

Fixes #14674

src/liballoc/lib.rs

@@ -92,6 +92,7 @@
 #![feature(unsize)]
 #![feature(drop_in_place)]
 #![feature(fn_traits)]
+#![feature(const_fn)]
 
 #![feature(needs_allocator)]
 
@@ -134,15 +135,6 @@ mod boxed_test;
 pub mod arc;
 pub mod rc;
 pub mod raw_vec;
+pub mod oom;
 
-/// Common out-of-memory routine
-#[cold]
-#[inline(never)]
-#[unstable(feature = "oom", reason = "not a scrutinized interface",
-           issue = "27700")]
-pub fn oom() -> ! {
-    // FIXME(#14674): This really needs to do something other than just abort
-    //                here, but any printing done must be *guaranteed* to not
-    //                allocate.
-    unsafe { core::intrinsics::abort() }
-}
+pub use oom::oom;