[ObjC] Add pre-commit tests [NFC]

Author: AZero13

clang/test/CodeGenObjC/constant-non-fragile-ivar-offset.m

@@ -1,6 +1,7 @@
 // RUN: %clang_cc1 -triple x86_64-apple-macosx10.14.0 -emit-llvm %s -o - | FileCheck %s
 
 // CHECK: @"OBJC_IVAR_$_StaticLayout.static_layout_ivar" = hidden constant i64 20
+// CHECK: @"OBJC_IVAR_$_StaticLayoutSubClass.static_layout_ivar2" = hidden global i64 24
 // CHECK: @"OBJC_IVAR_$_NotStaticLayout.not_static_layout_ivar" = hidden global i64 12
 
 @interface NSObject {
@@ -20,6 +21,18 @@ -(void)meth {
 }
 @end
 
+@interface StaticLayoutSubClass : StaticLayout
+@end
+
+@implementation StaticLayoutSubClass {
+  int static_layout_ivar2;
+}
+-(void)meth2 {
+  static_layout_ivar2 = 0;
+  // CHECK: load i64, ptr @"OBJC_IVAR_$_StaticLayoutSubClass
+}
+@end
+
 @interface NotNSObject {
   int these, might, change;
 }