add create directory api for iOS and macOS

src/objc_utils.cpp

@@ -334,3 +334,17 @@ void save_image_library(const std::string& path)
     }];
 #endif
 }
+
+bool apple_create_dir(const std::string& path)
+{
+    NSError* err = nil;
+    NSString* p = [NSString stringWithUTF8String:(path+"/").c_str()];
+    NSURL* url = [NSURL fileURLWithPath:p isDirectory:YES];
+    if (![[NSFileManager defaultManager] createDirectoryAtURL:url withIntermediateDirectories:YES attributes:nil error:&err])
+    {
+        LOG("error creating path: %s", path.c_str());
+        LOG("error creating path: %s", [[err description] cStringUsingEncoding:NSUTF8StringEncoding]);
+        return false;
+    }
+    return true;
+}