Simplify jemalloc setup

Using the new `override_allocator_on_supported_platforms` feature in
`tikv-jemalloc-sys v0.6.1` we can avoid the manual statics.

Author: madsmtm

src/driver.rs

@@ -13,10 +13,14 @@ extern crate rustc_interface;
 extern crate rustc_session;
 extern crate rustc_span;
 
-// See docs in https://github.com/rust-lang/rust/blob/HEAD/compiler/rustc/src/main.rs
-// about jemalloc.
+/// See docs in https://github.com/rust-lang/rust/blob/HEAD/compiler/rustc/src/main.rs
+/// and https://github.com/rust-lang/rust/pull/146627 for why we need this.
+///
+/// FIXME(madsmtm): This is loaded from the sysroot that was built with the other `rustc` crates
+/// above, instead of via Cargo as you'd normally do. This is currently needed for LTO due to
+/// https://github.com/rust-lang/cc-rs/issues/1613.
 #[cfg(feature = "jemalloc")]
-extern crate tikv_jemalloc_sys as jemalloc_sys;
+extern crate tikv_jemalloc_sys as _;
 
 use clippy_utils::sym;
 use declare_clippy_lint::LintListBuilder;
@@ -189,36 +193,6 @@ const BUG_REPORT_URL: &str = "https://github.com/rust-lang/rust-clippy/issues/ne
 
 #[expect(clippy::too_many_lines)]
 pub fn main() {
-    // See docs in https://github.com/rust-lang/rust/blob/HEAD/compiler/rustc/src/main.rs
-    // about jemalloc.
-    #[cfg(feature = "jemalloc")]
-    {
-        use std::os::raw::{c_int, c_void};
-
-        #[used]
-        static _F1: unsafe extern "C" fn(usize, usize) -> *mut c_void = jemalloc_sys::calloc;
-        #[used]
-        static _F2: unsafe extern "C" fn(*mut *mut c_void, usize, usize) -> c_int = jemalloc_sys::posix_memalign;
-        #[used]
-        static _F3: unsafe extern "C" fn(usize, usize) -> *mut c_void = jemalloc_sys::aligned_alloc;
-        #[used]
-        static _F4: unsafe extern "C" fn(usize) -> *mut c_void = jemalloc_sys::malloc;
-        #[used]
-        static _F5: unsafe extern "C" fn(*mut c_void, usize) -> *mut c_void = jemalloc_sys::realloc;
-        #[used]
-        static _F6: unsafe extern "C" fn(*mut c_void) = jemalloc_sys::free;
-
-        #[cfg(target_os = "macos")]
-        {
-            unsafe extern "C" {
-                fn _rjem_je_zone_register();
-            }
-
-            #[used]
-            static _F7: unsafe extern "C" fn() = _rjem_je_zone_register;
-        }
-    }
-
     let early_dcx = EarlyDiagCtxt::new(ErrorOutputType::default());
 
     rustc_driver::init_rustc_env_logger(&early_dcx);