[OpenACC][NFC] Update varlist-ast test to check serialization

I noticed while working on another test that I never used the PCH
trickery to get this to validate that serialization/deserialization
works correctly.  It DOES, but we weren't testing it with this test like
the others.

Author: erichkeane

clang/test/SemaOpenACC/compute-construct-varlist-ast.cpp

@@ -1,5 +1,12 @@
 // RUN: %clang_cc1 %s -fopenacc -Wno-openacc-deprecated-clause-alias -ast-dump | FileCheck %s
 
+// Test this with PCH.
+// RUN: %clang_cc1 %s -fopenacc -emit-pch -Wno-openacc-deprecated-clause-alias -o %t %s
+// RUN: %clang_cc1 %s -fopenacc -include-pch %t -Wno-openacc-deprecated-clause-alias -ast-dump-all | FileCheck %s
+
+#ifndef PCH_HELPER
+#define PCH_HELPER
+
 int Global;
 short GlobalArray[5];
 
@@ -435,7 +442,7 @@ void TemplUses(T t, U u, T*PointerParam) {
   // CHECK-NEXT: TemplateArgument type 'int'
   // CHECK-NEXT: BuiltinType{{.*}} 'int'
   // CHECK-NEXT: TemplateArgument type 'int[1]'
-  // CHECK-NEXT: ConstantArrayType{{.*}} 'int[1]' 1
+  // CHECK-NEXT: ConstantArrayType{{.*}} 'int[1]'{{.*}} 1
   // CHECK-NEXT: BuiltinType{{.*}} 'int'
   // CHECK-NEXT: ParmVarDecl{{.*}} used t 'int'
   // CHECK-NEXT: ParmVarDecl{{.*}} used u 'int *'
@@ -979,3 +986,4 @@ void Inst() {
   STempl<int> stempl;
   stempl.bar<int>();
 }
+#endif