[llvm-libc] Fix missing virtual destructor

[gchatelet]

Summary

This patch adds a virtual destructor to the Command class.

[gchatelet]

• Fix newline + remove =0

[sivachandra]

Address the comment before landing.

libc/utils/HdrGen/Command.cpp

2

Add license header and this is good to go.

[gchatelet]

• Address comments

[gchatelet]

• Fixed wrong description for the header

[gchatelet]

Thx !

libc/utils/HdrGen/CMakeLists.txt

 add_tablegen(libc-hdrgen llvm-libc
   Command.h
+  Command.cpp
   Generator.cpp
   Generator.h
   IncludeFileCommand.cpp
   IncludeFileCommand.h
   Main.cpp
   PublicAPICommand.cpp
   PublicAPICommand.h
 )

libc/utils/HdrGen/Command.h

public:
     ErrorReporter(llvm::SMLoc L, llvm::SourceMgr &SM) : Loc(L), SrcMgr(SM) {}
 
     void printFatalError(llvm::Twine Msg) const {
       SrcMgr.PrintMessage(Loc, llvm::SourceMgr::DK_Error, Msg);
       std::exit(1);
     }
   };
 
+  virtual ~Command();
+
   virtual void run(llvm::raw_ostream &OS, const ArgVector &Args,
                    llvm::StringRef StdHeader, llvm::RecordKeeper &Records,
                    const ErrorReporter &Reporter) const = 0;
 };
 
 } // namespace llvm_libc
 
 #endif // LLVM_LIBC_UTILS_HDRGEN_COMMAND_H

libc/utils/HdrGen/Command.cpp

+//===-------- Base class for header generation commands ---------*- 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "Command.h"
+
+namespace llvm_libc {
+
+Command::~Command() {}
+
+} // namespace llvm_libc