Fix some tests failing in --pass check mode

src/test/ui/lint/lint-exceeding-bitshifts.noopt.stderr

@@ -5,7 +5,7 @@ LL |     const N: i32 = T::N << 42;
    |                    ^^^^^^^^^^ attempt to shift left with overflow
    |
 note: the lint level is defined here
-  --> $DIR/lint-exceeding-bitshifts.rs:8:9
+  --> $DIR/lint-exceeding-bitshifts.rs:9:9
    |
 LL | #![warn(arithmetic_overflow, const_err)]
    |         ^^^^^^^^^^^^^^^^^^^

src/test/ui/lint/lint-exceeding-bitshifts.opt.stderr

@@ -5,7 +5,7 @@ LL |     const N: i32 = T::N << 42;
    |                    ^^^^^^^^^^ attempt to shift left with overflow
    |
 note: the lint level is defined here
-  --> $DIR/lint-exceeding-bitshifts.rs:8:9
+  --> $DIR/lint-exceeding-bitshifts.rs:9:9
    |
 LL | #![warn(arithmetic_overflow, const_err)]
    |         ^^^^^^^^^^^^^^^^^^^

src/test/ui/lint/lint-exceeding-bitshifts.opt_with_overflow_checks.stderr

@@ -5,7 +5,7 @@ LL |     const N: i32 = T::N << 42;
    |                    ^^^^^^^^^^ attempt to shift left with overflow
    |
 note: the lint level is defined here
-  --> $DIR/lint-exceeding-bitshifts.rs:8:9
+  --> $DIR/lint-exceeding-bitshifts.rs:9:9
    |
 LL | #![warn(arithmetic_overflow, const_err)]
    |         ^^^^^^^^^^^^^^^^^^^

src/test/ui/lint/lint-exceeding-bitshifts.rs

@@ -3,11 +3,11 @@
 //[opt]compile-flags: -O
 //[opt_with_overflow_checks]compile-flags: -C overflow-checks=on -O
 // build-pass
+// ignore-pass (test emits codegen-time warnings and verifies that they are not errors)
 
 #![crate_type="lib"]
 #![warn(arithmetic_overflow, const_err)]
-#![allow(unused_variables)]
-#![allow(dead_code)]
+
 
 pub trait Foo {
     const N: i32;