Test -Wpacked-non-pod does not emit warnings of "packed attribute is unnecessary"

clang/test/CodeGenCXX/warn-padded-packed.cpp

 // RUN: %clang_cc1 -triple=x86_64-none-none -Wpadded -Wpacked -verify=expected,top %s -emit-llvm-only
 // RUN: %clang_cc1 -triple=x86_64-none-none -Wpadded -Wpacked -verify=expected,abi15 -fclang-abi-compat=15 %s -emit-llvm-only
+// -Wpacked-non-pod itself should not emit the "packed attribute is unnecessary" warnings.
+// RUN: %clang_cc1 -triple=x86_64-none-none -Wpacked-non-pod -verify=top %s -emit-llvm-only
+// RUN: %clang_cc1 -triple=x86_64-none-none -Wpacked-non-pod -fclang-abi-compat=15 %s -emit-llvm-only
+
 
 struct S1 {
   char c;
   short s; // expected-warning {{padding struct 'S1' with 1 byte to align 's'}}
   long l; // expected-warning {{padding struct 'S1' with 4 bytes to align 'l'}}
 };
 
 struct S2 { // expected-warning {{padding size of 'S2' with 3 bytes to alignment boundary}}