Auto merge of #42123 - Mark-Simulacrum:revert-41967, r=alexcrichton
Auto merge of #42123 - Mark-Simulacrum:revert-41967, r=alexcrichton

Revert "Reenable opt-level 3"

This reverts commit 30383b2384864173b9238a121f8e83f8968f1e51, from #41967.

We believe that this is causing the failures when compiling rustc on 64 bit (which are probably segfaults).

cc @ishitatsuyuki

GBGamer/rust,graydon/rust,graydon/rust,aidancully/rust,GBGamer/rust,aidancully/rust,GBGamer/rust,GBGamer/rust,aidancully/rust,aidancully/rust,aidancully/rust,graydon/rust,GBGamer/rust,graydon/rust,graydon/rust,GBGamer/rust,GBGamer/rust,aidancully/rust,GBGamer/rust,graydon/rust