Auto merge of #45806 - alexcrichton:update-llvm-for-mips, r=michaelwoerister

rustbuild: Re-enable ThinLTO for MIPS

Now that the upstream LLVM bug is now fixed this commit cherry-picks the commit
onto our LLVM and then re-enables the ThinLTO paths for MIPS.

Closes #45654

src/bootstrap/builder.rs

@@ -625,8 +625,7 @@ pub fn cargo(&self,
 
             if mode != Mode::Libstd && // FIXME(#45320)
                self.config.rust_codegen_units.is_none() &&
-               self.build.is_rust_llvm(compiler.host) &&
-               !target.contains("mips") // FIXME(#45654)
+               self.build.is_rust_llvm(compiler.host)
             {
                 cargo.env("RUSTC_THINLTO", "1");
             }