Update the minimum external LLVM to 13

compiler/rustc_codegen_llvm/src/llvm_util.rs

@@ -92,16 +92,6 @@ unsafe fn configure_llvm(sess: &Session) {
             add("-generate-arange-section", false);
         }
 
-        // Disable the machine outliner by default in LLVM versions 11 and LLVM
-        // version 12, where it leads to miscompilation.
-        //
-        // Ref:
-        // - https://github.com/rust-lang/rust/issues/85351
-        // - https://reviews.llvm.org/D103167
-        if llvm_util::get_version() < (13, 0, 0) {
-            add("-enable-machine-outliner=never", false);
-        }
-
         match sess.opts.unstable_opts.merge_functions.unwrap_or(sess.target.merge_functions) {
             MergeFunctions::Disabled | MergeFunctions::Trampolines => {}
             MergeFunctions::Aliases => {