Previously, Windows builds were being produced without debug
information, leading to somewhat unhelpful backtraces etc.
without symbols.
This builds the symbols in (only for debug builds - I've
deliberately not touched release builds here) so gdextension
bugs are a little more tractable.
Test-Information:
Have been running this patch for weeks, and getting useful
traces out on the commandline, and useful debugging from
debuggers.
7f44a1b44e