[LLDB] Don't install the pretty backtrace handlers twice.

[JDevlieghere]

Summary

I noticed that currently we are printing LLVM's pretty stack trace
twice. The reason is that we're calling PrintStackTraceOnErrorSignal in
addition to InitLLVM, which besides some other useful things, also
register LLVM's pretty stack trace handler.

[JDevlieghere]

Fold ToolName into printHelp

[vsk]

Looks good to me!

[labath]

Cool. I saw that we print stack trace twice, but I thought that was because of the whole liblldb+lldb signal double installation. Thanks for fixing this.

lldb/tools/driver/Driver.cpp

 #include "lldb/API/SBReproducer.h"
 #include "lldb/API/SBStream.h"
 #include "lldb/API/SBStringList.h"
 
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/Format.h"
 #include "llvm/Support/InitLLVM.h"
 #include "llvm/Support/Path.h"
-#include "llvm/Support/PrettyStackTrace.h"
 #include "llvm/Support/Process.h"
 #include "llvm/Support/Signals.h"
 #include "llvm/Support/WithColor.h"
 #include "llvm/Support/raw_ostream.h"
 
 #include <algorithm>
 #include <atomic>
 #include <bitset>
if (capture || capture_path) {
     }
   }
 
   return llvm::None;
 }
 
 int main(int argc, char const *argv[])
 {
+  // Setup LLVM signal handlers and make sure we call llvm_shutdown() on
+  // destruction.
   llvm::InitLLVM IL(argc, argv);
 
-  // Print stack trace on crash.
-  llvm::StringRef ToolName = llvm::sys::path::filename(argv[0]);
-  llvm::sys::PrintStackTraceOnErrorSignal(ToolName);
-  llvm::PrettyStackTraceProgram X(argc, argv);
-
   // Parse arguments.
   LLDBOptTable T;
   unsigned MAI;
   unsigned MAC;
   ArrayRef<const char *> arg_arr = makeArrayRef(argv + 1, argc - 1);
   opt::InputArgList input_args = T.ParseArgs(arg_arr, MAI, MAC);
 
   if (input_args.hasArg(OPT_help)) {
-    printHelp(T, ToolName);
+    printHelp(T, llvm::sys::path::filename(argv[0]));
     return 0;
   }
 
   for (auto *arg : input_args.filtered(OPT_UNKNOWN)) {
     WithColor::warning() << "ignoring unknown option: " << arg->getSpelling()
                          << '\n';
   }