Fix crash reporter missing in Linux builds.

#rb Ben.Marsh (discussed)
#fyi Ben.Marsh, Matt.Kuhlenschmidt
#lockdown Nick.Penwarden

[CL 3622648 by Arciel Rekman in Main branch]

Engine/Source/Programs/CrashReportClient/Private/Linux/CrashReportClientMainLinux.cpp

@@ -0,0 +1,65 @@
+// Copyright 1998-2017 Epic Games, Inc. All Rights Reserved.
+
+#include "CoreMinimal.h"
+#include "Containers/StringConv.h"
+#include "Containers/UnrealString.h"
+#include "CoreGlobals.h"
+#include "Misc/OutputDeviceRedirector.h"
+#include "Misc/OutputDeviceError.h"
+#include "Misc/FeedbackContext.h"
+#include "CrashReportClientApp.h"
+#include "Linux/LinuxPlatformCrashContext.h"
+#include <locale.h>
+
+extern int32 ReportCrash(const FLinuxCrashContext& Context);	// FIXME: handle expose it someplace else?
+
+/**
+ * Because crash reporters can crash, too
+ */
+void CrashReporterCrashHandler(const FGenericCrashContext& GenericContext)
+{
+	// at this point we should already be using malloc crash handler (see PlatformCrashHandler)
+
+	const FLinuxCrashContext& Context = static_cast< const FLinuxCrashContext& >( GenericContext );
+
+	printf("CrashHandler: Signal=%d\n", Context.Signal);
+	const_cast< FLinuxCrashContext& >(Context).CaptureStackTrace();
+	if (GLog)
+	{
+		GLog->Flush();
+	}
+	if (GWarn)
+	{
+		GWarn->Flush();
+	}
+	if (GError)
+	{
+		GError->Flush();
+		GError->HandleError();
+	}
+	FPlatformMisc::RequestExit(true);
+}
+
+
+/**
+ * main(), called when the application is started
+ */
+int main(int argc, const char *argv[])
+{
+	FPlatformMisc::SetGracefulTerminationHandler();
+	FPlatformMisc::SetCrashHandler(CrashReporterCrashHandler);
+
+	FString SavedCommandLine;
+
+	setlocale(LC_CTYPE, "");
+	for (int32 Option = 1; Option < argc; Option++)
+	{
+		SavedCommandLine += TEXT(" ");
+		SavedCommandLine += UTF8_TO_TCHAR(argv[Option]);	// note: technically it depends on locale
+	}
+
+	// Run the app
+	RunCrashReportClient(*SavedCommandLine);
+
+	return 0;
+}