SCons: Add production=yes option to use production defaults

This is meant for users making custom builds to match the options used on
optimized, official builds.

This enables, on the platforms which support them:
- `use_static_cpp=yes` (portable binaries for Linux and Windows)
- `use_lto=yes` (link time optimizations - note: requires a lot of RAM!)
- `debug_symbols=no` (no debug symbols, smaller binaries)

Also abort when using MSVC with `production=yes`, as:
- It cannot optimize the GDScript VM like GCC or Clang do, leading to
  significant performance drops.
- Its LTO support is unreliable, at least used to trigger crashes last
  we tried it extensively.

All options can still be overridden if specified, and the `dev=yes` option
was changed to also support overrides.

platform/windows/detect.py

@@ -64,7 +64,7 @@ def get_opts():
         # XP support dropped after EOL due to missing API for IPv6 and other issues
         # Vista support dropped after EOL due to GH-10243
         ("target_win_version", "Targeted Windows version, >= 0x0601 (Windows 7)", "0x0601"),
-        EnumVariable("debug_symbols", "Add debugging symbols to release/release_debug builds", "yes", ("yes", "no")),
+        BoolVariable("debug_symbols", "Add debugging symbols to release/release_debug builds", True),
         EnumVariable("windows_subsystem", "Windows subsystem", "default", ("default", "console", "gui")),
         BoolVariable("separate_debug_symbols", "Create a separate file containing debugging symbols", False),
         ("msvc_version", "MSVC version to use. Ignored if VCINSTALLDIR is set in shell env.", None),