[SystemZ][z/OS] Add test of leading zero length bitfield in const/volatile struct

[abhina.sreeskantharajan]

LGTM, have a small nit

clang/test/CodeGen/SystemZ/zos-alignment.c

26

nit: spacing is off

clang/test/CodeGen/SystemZ/zos-alignment.c

 // RUN: %clang_cc1 -emit-llvm-only -triple s390x-none-zos -fdump-record-layouts %s | FileCheck %s --check-prefix=CHECK
 // RUN: %clang_cc1 -emit-llvm -triple s390x-none-zos %s -o - | FileCheck %s --check-prefix=DECL
 
 static int __attribute__((aligned(32))) v0;
 int __attribute__((aligned(32))) v1;
 typedef int __attribute__((aligned(32))) int32;
 static int32 v2;
 int32 v3;
 int f0() { return v0 + v1 + v2 + v3; }
 // DECL:      @v0 {{.*}} align 16
 // DECL-NEXT: @v1 {{.*}} align 32
 // DECL-NEXT: @v2 {{.*}} align 16
 // DECL-NEXT: @v3 {{.*}} align 32
 
+const struct cs0 {
+  unsigned long   :0;
+  long long        a;
+} CS0 = {};
+// CHECK:              0 | struct cs0
+// CHECK-NEXT:       0:- |   unsigned long
+// CHECK-NEXT:         0 |   long long a
+// CHECK-NEXT:           | [sizeof=8, align=8]
+
+volatile struct vs0 {
+  long            :0;
+  short           a;
+} VS0;
+// CHECK:              0 | struct vs0
+// CHECK-NEXT:       0:- |   long
+// CHECK-NEXT:         0 |   short a
+// CHECK-NEXT:           | [sizeof=2, align=2]
+
 struct s0 {
   short a:3;
   long b:5;
   int c:1;
   long d:10;
   char e:5;
 } S0;
 // CHECK:              0 | struct s0