[DNM] Enable fatal error backtraces

Author: al45tair

stdlib/public/runtime/Casting.cpp

@@ -385,7 +385,7 @@ SWIFT_NORETURN SWIFT_NOINLINE void
 swift::swift_dynamicCastFailure(const void *sourceType, const char *sourceName,
                                 const void *targetType, const char *targetName,
                                 const char *message) {
-  swift::fatalError(/* flags = */ 0,
+  swift::fatalError(/* flags = */ 1,
                     "Could not cast value of type '%s' (%p) to '%s' (%p)%s%s\n",
                     sourceName, sourceType, 
                     targetName, targetType, 

stdlib/public/runtime/Errors.cpp

@@ -400,6 +400,7 @@ bool swift::_swift_shouldReportFatalErrorsToDebugger() {
 /// Does not crash by itself.
 void swift::swift_reportError(uint32_t flags,
                               const char *message) {
+  #if 0
 #if defined(__APPLE__) && NDEBUG
   flags &= ~FatalErrorFlags::ReportBacktrace;
 #elif SWIFT_ENABLE_BACKTRACING
@@ -408,7 +409,8 @@ void swift::swift_reportError(uint32_t flags,
     flags &= ~FatalErrorFlags::ReportBacktrace;
   }
 #endif
-
+#endif
+  
   reportNow(flags, message);
   reportOnCrash(flags, message);
 }