C#: Fix MSVC dotnet dev_mode regression

[Repiteo]

A regression by #82729 brings back the erroneous behavior found in #79351. This is fixed by reimplementing the #else check in the ios export_plugin script

[bruvzg]

This change looks wrong, the export template checks are relevant for both Mono and non-Mono exports.

Probably should be something like:

#if defined(MODULE_MONO_ENABLED) && !defined(MACOS_ENABLED)
	// TODO: Remove this restriction when we don't rely on macOS tools to package up the native libraries anymore.
	r_error += TTR("Exporting to iOS when using C#/.NET is experimental and requires macOS.") + "\n";
	return false;
#else

#if defined(MODULE_MONO_ENABLED)
	// iOS export is still a work in progress, keep a message as a warning.
	r_error += TTR("Exporting to iOS when using C#/.NET is experimental.") + "\n";
#endif

	String err;
	bool valid = false;
	// Look for export templates (first official, and if defined custom templates).
	bool dvalid = exists_export_template("ios.zip", &err);
	bool rvalid = dvalid; // Both in the same ZIP.
	if (p_preset->get("custom_template/debug") != "") {
		dvalid = FileAccess::exists(p_preset->get("custom_template/debug"));
		if (!dvalid) {
			err += TTR("Custom debug template not found.") + "\n";
		}
	}
	if (p_preset->get("custom_template/release") != "") {
		rvalid = FileAccess::exists(p_preset->get("custom_template/release"));
		if (!rvalid) {
			err += TTR("Custom release template not found.") + "\n";
		}
	}
	valid = dvalid || rvalid;
	r_missing_templates = !valid;
	if (!err.is_empty()) {
		r_error += err;
	}

	return valid;
#endif

[Repiteo]

Oop, I must've assumed the macos check returned early too. Got a fixed version up now

[akien-mga]

Thanks!