Raise an informative error when running on macOS under Rosetta 2.

Current users only get a cryptic "Illegal instruction" crash.

Context: https://github.com/deepmind/mujoco/issues/611
PiperOrigin-RevId: 491705647
Change-Id: I1285897a36e858300ee3d125957e90754be9a7f7

simulate/macos_gui.mm

@@ -0,0 +1,44 @@
+// Copyright 2022 DeepMind Technologies Limited
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <sstream>
+#include <string>
+
+#include <Cocoa/Cocoa.h>
+
+std::string GetSavePath(const char* filename) {
+  NSSavePanel* panel = [NSSavePanel savePanel];
+  NSURL* userDocumentsDir = [NSFileManager.defaultManager URLsForDirectory:NSDocumentDirectory
+                                                          inDomains:NSUserDomainMask].firstObject;
+  [panel setDirectoryURL:userDocumentsDir];
+  [panel setNameFieldStringValue:[NSString stringWithUTF8String:filename]];
+  if ([panel runModal] == NSModalResponseOK) {
+    std::ostringstream s;
+    s << [panel.URL.path cStringUsingEncoding:NSUTF8StringEncoding];
+    return s.str();
+  } else {
+    return "";
+  }
+}
+
+#ifdef __AVX__
+void DisplayErrorDialogBox(const char* title, const char* msg) {
+  NSAlert *alert = [[[NSAlert alloc] init] autorelease];
+  [alert setMessageText:[NSString stringWithUTF8String:title]];
+  [alert setInformativeText:[NSString stringWithUTF8String:msg]];
+  [alert setAlertStyle:NSAlertStyleCritical];
+  [alert addButtonWithTitle:@"Exit"];
+  [alert runModal];
+}
+#endif