Resurrect error.log and error.dmp file output when the engine crashes (LYN-3873) (#811)

Resurrect error.log and error.dmp file output when the engine crashes (LYN-3873). This was recently removed as part of 96b85e6813920554f7dfdc7752c1dd4452919b92

Code/CryEngine/CrySystem/DllMain.cpp

@@ -14,6 +14,7 @@
 #include "CrySystem_precompiled.h"
 #include "System.h"
 #include <AZCrySystemInitLogSink.h>
+#include "DebugCallStack.h"
 
 #if defined(AZ_RESTRICTED_PLATFORM)
 #undef AZ_RESTRICTED_SECTION
@@ -87,6 +88,16 @@ CRYSYSTEM_API ISystem* CreateSystemInterface(const SSystemInitParams& startupPar
         startupParams.pUserCallback->OnSystemConnect(pSystem);
     }
 
+#if defined(WIN32)
+    // Environment Variable to signal we don't want to override our exception handler - our crash report system will set this
+    auto envVar = AZ::Environment::FindVariable<bool>("ExceptionHandlerIsSet");
+    const bool handlerIsSet = (envVar && *envVar);
+    if (!handlerIsSet)
+    {
+        ((DebugCallStack*)IDebugCallStack::instance())->installErrorHandler(pSystem);
+    }
+#endif
+
     bool retVal = false;
     {
         AZ::Debug::StartupLogSinkReporter<AZ::Debug::CrySystemInitLogSink> initLogSink;