Compile Servo with the latest version of rust stable (#30831)

This completes the transition to compiling Servo with rust stable. Some
nightly-only features are still used when compiling the `script` and
`crown` crates, as well as for some style unit tests. These will likely
break with newer compiler versions, but `crown` can be disabled for them
conditionally. This is just the first step.

This has some caveats:

1. We need to disable setting up the special linker on Linux. The -Z
   option isn't supported with stable rust so using this is out --
   meanwhile we can't be sure that lld is installed on most systems.
2. `cargo fmt` still uses some unstable options, so we need to rely on
   the unstable toolchain just for running `fmt`. The idea is to fix this
   gradually.

1 files changed, 1 insertions, 6 deletions

diff --git a/components/script/dom/testbinding.rs b/components/script/dom/testbinding.rs
index 5e2748ac692..94af8390041 100644
--- a/components/script/dom/testbinding.rs
+++ b/components/script/dom/testbinding.rs
@@ -5,7 +5,6 @@
 // check-tidy: no specs after this line
 
 use std::borrow::ToOwned;
-use std::ptr;
 use std::ptr::NonNull;
 use std::rc::Rc;
 
@@ -1043,11 +1042,7 @@ impl TestBindingMethods for TestBinding {
 
     #[allow(unsafe_code)]
     fn CrashHard(&self) {
-        static READ_ONLY_VALUE: i32 = 0;
-        unsafe {
-            let p: *mut u32 = &READ_ONLY_VALUE as *const _ as *mut _;
-            ptr::write_volatile(p, 0xbaadc0de);
-        }
+        unsafe { std::ptr::null_mut::<i32>().write(42) }
     }
 
     fn AdvanceClock(&self, ms: i32) {