[TableGen] emitStringLiteralDef: Pad trailing '\0' at the end of char array.

[chapuni]

Summary

Fixup for https://reviews.llvm.org/D73044
String literal has an implicit terminator '\0'. This commit adjusts char array
to long literal.

This causes difference of artifacts between -long-string-literals=true
and false.

[chapuni]

I will rebase this after D126135 will be applied.

[rnk]

lgtm

llvm/utils/TableGen/SequenceToOffsetTable.h

 //===-- SequenceToOffsetTable.h - Compress similar sequences ----*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
if (EmitLongStrLiterals) {
       OS << "\n#ifdef __GNUC__\n"
          << "#pragma GCC diagnostic push\n"
          << "#pragma GCC diagnostic ignored \"-Woverlength-strings\"\n"
          << "#endif\n"
          << Decl << " = {\n";
     } else {
       OS << Decl << " = {\n";
       emit(OS, printChar, "0");
-      OS << "\n};\n\n";
+      OS << "  0\n};\n\n";
       return;
     }
     for (auto I : Seqs) {
       OS << "  /* " << I.second << " */ \"";
       for (auto C : I.first) {
         printStrLitEscChar(OS, C);
       }
       OS << "\\0\"\n";