Tools emit the bug report URL on crash

When Clang crashes a useful message is output:

"PLEASE submit a bug report to https://bugs.llvm.org/ and include the
crash backtrace, preprocessed source, and associated run script."

A similar message is now output for all tools.

Differential Revision: https://reviews.llvm.org/D74324

include/llvm/Support/PrettyStackTrace.h

@@ -37,6 +37,10 @@ namespace llvm {
   /// \see PrettyStackTraceEntry
   void EnablePrettyStackTraceOnSigInfoForThisThread(bool ShouldEnable = true);
 
+  /// Replaces the generic bug report message that is output upon
+  /// a crash.
+  void setBugReportMsg(const char *Msg);
+
   /// PrettyStackTraceEntry - This class is used to represent a frame of the
   /// "pretty" stack trace that is dumped when a program crashes. You can define
   /// subclasses of this and declare them on the program stack: when they are

lib/Support/PrettyStackTrace.cpp

@@ -142,9 +142,17 @@ using CrashHandlerStringStorage =
 static CrashHandlerStringStorage crashHandlerStringStorage;
 #endif
 
+static const char *BugReportMsg =
+    "PLEASE submit a bug report to " BUG_REPORT_URL
+    " and include the crash backtrace.\n";
+
+void llvm::setBugReportMsg(const char *Msg) { BugReportMsg = Msg; }
+
 /// This callback is run if a fatal signal is delivered to the process, it
 /// prints the pretty stack trace.
 static void CrashHandler(void *) {
+  errs() << BugReportMsg ;
+
 #ifndef __APPLE__
   // On non-apple systems, just emit the crash stack trace to stderr.
   PrintCurStackTrace(errs());