Auto merge of #51687 - japaric:gh51671, r=alexcrichton

translate / export weak lang items

see #51671 for details

fixes #51671
fixes #51342

r? @michaelwoerister or @alexcrichton

src/test/run-make-fulldeps/issue-51671/Makefile

@@ -0,0 +1,13 @@
+-include ../tools.mk
+
+ifdef IS_WINDOWS
+# Do nothing on MSVC.
+all:
+	exit 0
+else
+all:
+	$(RUSTC) --emit=obj app.rs
+	nm $(TMPDIR)/app.o | $(CGREP) rust_begin_unwind
+	nm $(TMPDIR)/app.o | $(CGREP) rust_eh_personality
+	nm $(TMPDIR)/app.o | $(CGREP) rust_oom
+endif

src/test/run-make-fulldeps/issue-51671/app.rs

@@ -0,0 +1,28 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![crate_type = "bin"]
+#![feature(lang_items)]
+#![feature(panic_implementation)]
+#![no_main]
+#![no_std]
+
+use core::panic::PanicInfo;
+
+#[panic_implementation]
+fn panic(_: &PanicInfo) -> ! {
+    loop {}
+}
+
+#[lang = "eh_personality"]
+fn eh() {}
+
+#[lang = "oom"]
+fn oom() {}