Fix test case on linux

Author: aschwaighofer

test/IRGen/weak_class_protocol.sil

@@ -15,7 +15,7 @@ protocol Foo: class { }
 // CHECK:         store i8** [[WTABLE]], i8*** [[WTABLE_SLOT]], align 8
 // CHECK:         [[INSTANCE_SLOT:%.*]] = getelementptr inbounds { %swift.weak, i8** }, { %swift.weak, i8** }* %0, i32 0, i32 0
 // CHECK-objc:    call void @swift_unknownWeakAssign(%swift.weak* [[INSTANCE_SLOT]], %objc_object* [[INSTANCE]]) {{#[0-9]+}}
-// CHECK-native:  call void @swift_weakAssign(%swift.weak* [[INSTANCE_SLOT]], %swift.refcounted* [[INSTANCE]]) {{#[0-9]+}}
+// CHECK-native:  call %swift.weak* @swift_weakAssign(%swift.weak* [[INSTANCE_SLOT]], %swift.refcounted* [[INSTANCE]]) {{#[0-9]+}}
 // CHECK:         ret void
 // CHECK:       }
 sil @store_weak : $@convention(thin) (@owned Foo?) -> @out @sil_weak Foo? {