[backtrace-sys] stub interface for host builds

Change-Id: I6ddb987909884f0d9a628d3e275ad8781159e3d4
diff --git a/rustc_deps/tiny_mirrors/backtrace-sys/src/lib.rs b/rustc_deps/tiny_mirrors/backtrace-sys/src/lib.rs
index c679081..4e22ef2 100644
--- a/rustc_deps/tiny_mirrors/backtrace-sys/src/lib.rs
+++ b/rustc_deps/tiny_mirrors/backtrace-sys/src/lib.rs
@@ -1,3 +1,44 @@
 // Copyright 2018 The Fuchsia Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
+
+#![feature(libc)]
+extern crate libc;
+pub struct backtrace_state;
+
+use libc::uintptr_t;
+use std::os::raw::{c_void, c_char, c_int};
+
+pub type backtrace_syminfo_callback =
+    extern fn(data: *mut c_void,
+              pc: uintptr_t,
+              symname: *const c_char,
+              symval: uintptr_t,
+              symsize: uintptr_t);
+pub type backtrace_full_callback =
+    extern fn(data: *mut c_void,
+              pc: uintptr_t,
+              filename: *const c_char,
+              lineno: c_int,
+              function: *const c_char) -> c_int;
+pub type backtrace_error_callback =
+    extern fn(data: *mut c_void,
+              msg: *const c_char,
+              errnum: c_int);
+
+pub fn backtrace_create_state(filename: *const c_char,
+                              threaded: c_int,
+                              error: backtrace_error_callback,
+                              data: *mut c_void) -> *mut backtrace_state {std::ptr::null_mut::<backtrace_state>()}
+
+pub fn backtrace_syminfo(state: *mut backtrace_state,
+                          addr: uintptr_t,
+                          cb: backtrace_syminfo_callback,
+                          error: backtrace_error_callback,
+                          data: *mut c_void) -> c_int {0}
+
+pub fn backtrace_pcinfo(state: *mut backtrace_state,
+                        addr: uintptr_t,
+                        cb: backtrace_full_callback,
+                        error: backtrace_error_callback,
+                        data: *mut c_void) -> c_int {0}
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