Package macOS releases as a universal binary.

* Minimum macOS version is raised to 10.11.
* App bundles ship 3 versions of the runtime and engine binaries,
  and a fat launcher that selects the appropriate runtime/apphost.
* Mono is used for macOS 10.11 - 10.14, or if OPENRA_PREFER_MONO
  environment variable has been set.

packaging/macos/checkmono.c

@@ -0,0 +1,73 @@
+/*
+ * Copyright 2007-2022 The OpenRA Developers (see AUTHORS)
+ * This file is part of OpenRA, which is free software. It is made
+ * available to you under the terms of the GNU General Public License
+ * as published by the Free Software Foundation. For more information,
+ * see COPYING.
+ */
+
+//
+// NOTE: Mono.framework only ships intel dylibs, so cannot be loaded by the arm64 slice of the Launcher utility.
+// Splitting checkmono into its own intel-only utility allows it to be called through rosetta if the user
+// wants to force the game to run under mono-through-rosetta.
+//
+// Based on https://github.com/mono/monodevelop/blob/main/main/build/MacOSX/monostub.mm and https://github.com/mono/monodevelop/blob/main/main/build/MacOSX/monostub-utils.h
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <dlfcn.h>
+
+#define SYSTEM_MONO_PATH "/Library/Frameworks/Mono.framework/Versions/Current/"
+#define SYSTEM_MONO_MIN_VERSION "6.4"
+
+typedef char *(* mono_get_runtime_build_info)(void);
+
+int main(int argc, char **argv)
+{
+	void *libmono = dlopen(SYSTEM_MONO_PATH "lib/libmonosgen-2.0.dylib", RTLD_LAZY);
+	if (libmono == NULL)
+	{
+		fprintf (stderr, "Failed to load libmonosgen-2.0.dylib: %s\n", dlerror());
+		return 1;
+	}
+
+	mono_get_runtime_build_info _mono_get_runtime_build_info = (mono_get_runtime_build_info)dlsym(libmono, "mono_get_runtime_build_info");
+	if (!_mono_get_runtime_build_info)
+	{
+		fprintf(stderr, "Could not load mono_get_runtime_build_info(): %s\n", dlerror());
+		return 1;
+	}
+
+	char *version = _mono_get_runtime_build_info();
+	char *req_end, *end;
+	long req_val, val;
+	char *req_version = SYSTEM_MONO_MIN_VERSION;
+
+	while (*req_version && *version)
+	{
+		req_val = strtol(req_version, &req_end, 10);
+		if (req_version == req_end || (*req_end && *req_end != '.'))
+		{
+			fprintf(stderr, "Bad version requirement string '%s'\n", req_end);
+			return 1;
+		}
+
+		val = strtol(version, &end, 10);
+		if (version == end || val < req_val)
+			return 1;
+
+		if (val > req_val)
+			return 0;
+
+		if (*req_end == '.' && *end != '.')
+			return 1;
+
+		req_version = req_end;
+		if (*req_version)
+			req_version++;
+
+		version = end + 1;
+	}
+
+	return 0;
+}