`-use-separate-modules` default on Windows only

src/build_settings.cpp

@@ -1658,7 +1658,7 @@ gb_internal void init_build_context(TargetMetrics *cross_target, Subtarget subta
 
 	bc->optimization_level = gb_clamp(bc->optimization_level, -1, 3);
 
-#if !defined(GB_SYSTEM_OSX)
+#if defined(GB_SYSTEM_WINDOWS)
 	if (bc->optimization_level <= 0) {
 		if (!is_arch_wasm()) {
 			bc->use_separate_modules = true;

src/main.cpp

@@ -2314,7 +2314,7 @@ gb_internal void print_show_help(String const arg0, String const &command) {
 		print_usage_line(1, "-use-separate-modules");
 		print_usage_line(2, "The backend generates multiple build units which are then linked together.");
 		print_usage_line(2, "Normally, a single build unit is generated for a standard project.");
-		print_usage_line(2, "This is the default behaviour for '-o:none' and '-o:minimal' builds");
+		print_usage_line(2, "This is the default behaviour on Windows for '-o:none' and '-o:minimal' builds.");
 		print_usage_line(0, "");
 
 	}