Rewritten objc.m to use Objective-C objects (NSData, NSString and NSFileHandle) and provided build instructions using clang on both OS X and Linux.

o/objc.m

@@ -1,7 +1,21 @@
-#import <Cocoa/Cocoa.h>
+/*
+ Build on OS X: 
+ clang -framework Foundation -fobjc-arc objc.m -o objc
  
-int main(int argc, char *argv[])
+ Build on Linux with GNUstep:
+ clang `gnustep-config --objc-flags` `gnustep-config --base-libs` -fobjc-nonfragile-abi -fobjc-arc objc.m -o objc
+ */
+
+#import <Foundation/Foundation.h>
+
+int main(void)
 {
-    NSLog(@"Hello, World!\n");
+    @autoreleasepool
-	return 0;
+    {
+        NSFileHandle *_stderr = [NSFileHandle fileHandleWithStandardError];
+        NSString *string = @"hello, world\n";
+        NSData *data = [string dataUsingEncoding:[NSString defaultCStringEncoding]];
+        [_stderr writeData:data];
+    }
+    return EXIT_SUCCESS;
 }