sim: Prepare C++ side for Python 3

Python 3 uses wide strings instead of ordinary strings for many
APIs. Add the necessary conversions to comply with the new API.

Change-Id: I6f45c9c532537d50d54b542f34eb8fd8cb375874
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/15977
Reviewed-by: Gabe Black <gabeblack@google.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>

src/sim/main.cc

@@ -45,7 +45,14 @@ main(int argc, char **argv)
     // Initialize m5 special signal handling.
     initSignals();
 
+#if PY_MAJOR_VERSION >= 3
+    std::unique_ptr<wchar_t[], decltype(&PyMem_RawFree)> program(
+        Py_DecodeLocale(argv[0], NULL),
+        &PyMem_RawFree);
+    Py_SetProgramName(program.get());
+#else
     Py_SetProgramName(argv[0]);
+#endif
 
     // initialize embedded Python interpreter
     Py_Initialize();