Import backtrace-cpp and integrate it into our main executable

Upstream release
https://github.com/bombela/backward-cpp/archive/v1.3.tar.gz

external/backtrace-cpp/backward.cpp

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+// Pick your poison.
+//
+// On GNU/Linux, you have few choices to get the most out of your stack trace.
+//
+// By default you get:
+//	- object filename
+//	- function name
+//
+// In order to add:
+//	- source filename
+//	- line and column numbers
+//	- source code snippet (assuming the file is accessible)
+
+// Install one of the following library then uncomment one of the macro (or
+// better, add the detection of the lib and the macro definition in your build
+// system)
+
+// - apt-get install libdw-dev ...
+// - g++/clang++ -ldw ...
+// #define BACKWARD_HAS_DW 1
+
+// - apt-get install binutils-dev ...
+// - g++/clang++ -lbfd ...
+// #define BACKWARD_HAS_BFD 1
+
+#include "backward.hpp"
+
+namespace backward {
+
+backward::SignalHandling sh;
+
+} // namespace backward