ggml : Print backtrace on uncaught C++ exceptions (ggml/1232)

The goal is to have what users call "full logs" contain the backtrace.

This is registered upon ggml_init. Also fixes a minor fd leak on Linux.

ggml/src/CMakeLists.txt

@@ -196,6 +196,7 @@ add_library(ggml-base
             ../include/ggml-opt.h
             ../include/gguf.h
             ggml.c
+            ggml.cpp
             ggml-alloc.c
             ggml-backend.cpp
             ggml-opt.cpp