Add Assume custom MIR.

Author: cjgillot

core/src/intrinsics/mir.rs

@@ -357,6 +357,8 @@ define!("mir_unwind_resume",
 
 define!("mir_storage_live", fn StorageLive<T>(local: T));
 define!("mir_storage_dead", fn StorageDead<T>(local: T));
+#[cfg(not(bootstrap))]
+define!("mir_assume", fn Assume(operand: bool));
 define!("mir_deinit", fn Deinit<T>(place: T));
 define!("mir_checked", fn Checked<T>(binop: T) -> (T, bool));
 define!("mir_len", fn Len<T>(place: T) -> usize);