Rollup merge of rust-lang#127857 - tbu-:pr_deprecated_safe_todo, r=petrochenkov

Allow to customize `// TODO:` comment for deprecated safe autofix

Relevant for the deprecation of `CommandExt::before_exit` in rust-lang#125970.

Tracking:
- rust-lang#124866

Author: matthiaskrgr

Diff for: std/src/env.rs

@@ -355,7 +355,13 @@ impl Error for VarError {
 /// }
 /// assert_eq!(env::var(key), Ok("VALUE".to_string()));
 /// ```
-#[rustc_deprecated_safe_2024]
+#[cfg_attr(bootstrap, rustc_deprecated_safe_2024)]
+#[cfg_attr(
+    not(bootstrap),
+    rustc_deprecated_safe_2024(
+        audit_that = "the environment access only happens in single-threaded code"
+    )
+)]
 #[stable(feature = "env", since = "1.0.0")]
 pub unsafe fn set_var<K: AsRef<OsStr>, V: AsRef<OsStr>>(key: K, value: V) {
     let (key, value) = (key.as_ref(), value.as_ref());
@@ -419,7 +425,13 @@ pub unsafe fn set_var<K: AsRef<OsStr>, V: AsRef<OsStr>>(key: K, value: V) {
 /// }
 /// assert!(env::var(key).is_err());
 /// ```
-#[rustc_deprecated_safe_2024]
+#[cfg_attr(bootstrap, rustc_deprecated_safe_2024)]
+#[cfg_attr(
+    not(bootstrap),
+    rustc_deprecated_safe_2024(
+        audit_that = "the environment access only happens in single-threaded code"
+    )
+)]
 #[stable(feature = "env", since = "1.0.0")]
 pub unsafe fn remove_var<K: AsRef<OsStr>>(key: K) {
     let key = key.as_ref();