Auto merge of #1133 - RalfJung:compile-fail-opt, r=RalfJung

compile-fail tests work with optimizations now

Author: bors

tests/compile-fail/validity/nonzero.rs

@@ -1,3 +1,4 @@
+// compile-flags: -Zmir-opt-level=1
 #![feature(rustc_attrs)]
 #![allow(unused_attributes)]
 

tests/compiletest.rs

@@ -69,9 +69,7 @@ fn compile_fail(path: &str, target: &str, opt: bool) {
 
     let mut flags = Vec::new();
     if opt {
-        // FIXME: Opt level 2 ICEs during stack trace generation.
-        // See https://github.com/rust-lang/rust/issues/66077.
-        flags.push("-Zmir-opt-level=1".to_owned());
+        flags.push("-Zmir-opt-level=3".to_owned());
     }
 
     run_tests("compile-fail", path, target, flags);