libxl: abort on memory allocation errors

Use abort() instead of just _exit() in libxl__alloc_failed(). This
is more friendly for debugging, as it will trap into debugger,
systemd-coredump will collect coredump/backtrace etc. It's much more
useful than just "libxl: FATAL ERROR: memory allocation failure (...)"
message without context where it actually failed.

Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Acked-by: Anthony PERARD <anthony.perard@citrix.com>

tools/libs/light/libxl_internal.c

@@ -36,7 +36,7 @@ void libxl__alloc_failed(libxl_ctx *ctx, const char *func,
     }
 
     fflush(stderr);
-    _exit(-1);
+    abort();
 #undef M_NSIZE
 #undef M_SIZE
 #undef M