Auto merge of #28564 - bjorn3:patch-1, r=jdm

Update script_plugin for rust-lang/rust#85296

This will update the script_plugin for the plugin interface changes in rust-lang/rust#85296.

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `___` with appropriate data: -->
- [ ] `./mach build -d` does not report any errors
- [ ] `./mach test-tidy` does not report any errors
- [ ] These changes fix #___ (GitHub issue number if applicable)

<!-- Either: -->
- [ ] There are tests for these changes OR
- [x] These changes do not require tests because it is a fix for rustc changes.

components/script_plugins/lib.rs

@@ -9,7 +9,6 @@
 
 #![deny(unsafe_code)]
 #![feature(plugin)]
-#![feature(plugin_registrar)]
 #![feature(rustc_private)]
 #![cfg(feature = "unrooted_must_root_lint")]
 
@@ -34,9 +33,9 @@ use rustc_span::source_map::{ExpnKind, MacroKind, Span};
 use rustc_span::symbol::sym;
 use rustc_span::symbol::Symbol;
 
-#[allow(deprecated)]
-#[plugin_registrar]
-pub fn plugin_registrar(reg: &mut Registry) {
+#[allow(unsafe_code)] // #[no_mangle] is unsafe
+#[no_mangle]
+fn __rustc_plugin_registrar(reg: &mut Registry) {
     registrar(reg)
 }
 

rust-toolchain

@@ -1 +1 @@
-nightly-2021-07-17
+nightly-2021-08-13