Rollup merge of rust-lang#154972 - chorman0773:return_address, r=Mark-Simulacrum

Implement `core::arch::return_address` and tests

Tracking issue: rust-lang#154966

Implements libs-team#768

Author: JonathanBrouwer

src/intrinsics/mod.rs

@@ -1523,6 +1523,12 @@ fn codegen_regular_intrinsic_call<'tcx>(
             fx.bcx.set_cold_block(fx.bcx.current_block().unwrap());
         }
 
+        sym::return_address => {
+            let val = fx.bcx.ins().get_return_address(fx.pointer_type);
+            let val = CValue::by_val(val, ret.layout());
+            ret.write_cvalue(fx, val);
+        }
+
         // Unimplemented intrinsics must have a fallback body. The fallback body is obtained
         // by converting the `InstanceKind::Intrinsic` to an `InstanceKind::Item`.
         _ => {