Auto merge of #51165 - SimonSapin:opt2, r=alexcrichton

Revert "Set opt-level to 3"

This reverts commit aad9840a.

Level 3 (possibly indirectly, the underlying bug might be in XCode’s linker) causes unit tests to sefault when compiled with some versions of XCode: https://github.com/rust-lang/rust/issues/50867

It also appears to cause some segfaults on Windows: https://github.com/rust-lang/rust/pull/50329#issuecomment-386853473, and regressions in some rustc performance benchmarks: https://github.com/rust-lang/rust/pull/50329#issuecomment-388084894

src/Cargo.toml

@@ -40,6 +40,13 @@ members = [
   "tools/rls/test_data/workspace_symbol",
 ]
 
+# Curiously, libtest will segfault if compiled with opt-level=3
+# with some versions of XCode: https://github.com/rust-lang/rust/issues/50867
+[profile.release]
+opt-level = 2
+[profile.bench]
+opt-level = 2
+
 # These options are controlled from our rustc wrapper script, so turn them off
 # here and have them controlled elsewhere.
 [profile.dev]