-x objective-c throws System.ArgumentNullException about nclang HOT 8 OPEN

/sources/nclang/NClang/bin/Debug/net462$ ls
NClang.dll  NClang.pdb  sample.m  x.cs  x.exe
/sources/nclang/NClang/bin/Debug/net462$ cat x.cs
using System;
using NClang;

public class Driver
{
	public static void Main (string [] args)
	{
		var index = ClangService.CreateIndex();
		var trans = index.ParseTranslationUnit("sample.m", args, null, TranslationUnitFlags.SingleFileParse);
	}
}

/sources/nclang/NClang/bin/Debug/net462$ csc x.cs -r:NClang.dll
Microsoft (R) Visual C# Compiler version 3.4.0-beta4-19569-03 (82f2e254)
Copyright (C) Microsoft Corporation. All rights reserved.

/sources/nclang/NClang/bin/Debug/net462$ mono x.exe -x objective-c
/sources/nclang/NClang/bin/Debug/net462$ cat sample.m
#import <Foundation/Foundation.h>

int main (int argc, const char * argv[]) {
   NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

   NSLog (@"hello world");
   [pool drain];
   return 0;
}

        ClangTranslationUnit tu;
        var errors = index.ParseTranslationUnit("Sample.m", Flags, null, TranslationUnitFlags.SingleFileParse, out tu);
        Console.WriteLine (errors);

~/Desktop/AnotherTry/bin/Debug$ cat Sample.m 
#import <Foundation/Foundation.h>

int main (int argc, const char * argv[]) {
   NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

   NSLog (@"hello world");
   [pool drain];
   return 0;
}~/Desktop/AnotherTry/bin/Debug$ clang -x objective-c Sample.m 
Sample.m:1:9: fatal error: 'Foundation/Foundation.h' file not found
#import <Foundation/Foundation.h>
        ^~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.

~/Desktop/AnotherTry/bin/Debug$ clang -target ./target/arm64-apple-darwin14 -arch arm64 -x objective-c -fmodules -isysroot ./sdk/ Sample.m
./target/arm64-apple-darwin14-ld: error while loading shared libraries: libtapi.so: cannot open shared object file: No such file or directory