debuginfo: Generate cross-crate unique type identifiers for debuginfo types.

With this change, rustc creates a unique type identifier for types in debuginfo. These type identifiers are used by LLVM to correctly handle link-time-optimization scenarios but also help rustc with dealing with inlining from other crates. For more information, see the documentation block at the top of librustc/middle/trans/debuginfo.rs.

Fixes #13681.

src/test/auxiliary/cross_crate_debuginfo_type_uniquing.rs

@@ -0,0 +1,26 @@
+// Copyright 2013-2014 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.
+
+// no-prefer-dynamic
+#![crate_type = "rlib"]
+// compile-flags:-g
+
+struct S1;
+
+impl S1 {
+    fn f(&mut self) { }
+}
+
+
+struct S2;
+
+impl S2 {
+    fn f(&mut self) { }
+}

src/test/debuginfo/cross-crate-type-uniquing.rs

@@ -0,0 +1,24 @@
+// Copyright 2013-2014 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.
+
+// ignore-android: FIXME(#10381)
+
+// aux-build:cross_crate_debuginfo_type_uniquing.rs
+extern crate cross_crate_debuginfo_type_uniquing;
+
+// no-prefer-dynamic
+// compile-flags:-g -Zlto
+
+pub struct C;
+pub fn p() -> C {
+    C
+}
+
+fn main() { }