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

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.

Differential Revision: https://reviews.llvm.org/D126136

llvm/utils/TableGen/SequenceToOffsetTable.h

@@ -173,7 +173,7 @@ public:
     if (!EmitLongStrLiterals) {
       OS << Decl << " = {\n";
       emit(OS, printChar, "0");
-      OS << "\n};\n\n";
+      OS << "  0\n};\n\n";
       return;
     }