[EXPERIMENTAL] Try needs-unwind

tests/ui/debuginfo/backtrace-line-tables-only.rs

@@ -5,6 +5,7 @@
 //@ ignore-windows
 //@ run-pass
 //@ compile-flags: -Cdebuginfo=line-tables-only
+//@ needs-unwind
 #![feature(backtrace_frames)]
 
 use std::backtrace::{self, Backtrace};
@@ -32,7 +33,6 @@ fn assert_contains(
     // FIXME(jieyouxu): fix this ugly fragile test when `BacktraceFrame` has accessors like...
     // `symbols()`.
     let backtrace = format!("{:#?}", backtrace);
-    eprintln!("{}", backtrace);
     assert!(backtrace.contains(expected_name), "backtrace does not contain expected name {}", expected_name);
     assert!(backtrace.contains(expected_file), "backtrace does not contain expected file {}", expected_file);
     assert!(backtrace.contains(&expected_line.to_string()), "backtrace does not contain expected line {}", expected_line);
@@ -50,6 +50,7 @@ fn main() {
     let mut backtrace: Option<Backtrace> = None;
     unsafe { line_tables_only_foo(store_backtrace, addr_of_mut!(backtrace).cast::<c_void>()) };
     let backtrace = backtrace.expect("backtrace");
+    eprintln!("{:#?}", backtrace);
     assert_contains(&backtrace, "line_tables_only_foo", "rust_test_helpers.c", 435);
     assert_contains(&backtrace, "line_tables_only_bar", "rust_test_helpers.c", 439);
     assert_contains(&backtrace, "line_tables_only_baz", "rust_test_helpers.c", 443);