[clang][Module][AIX] Mark test unsupported since objc doesn't have xcoff support

[clang][Module][AIX] Mark test unsupported since objc doesn't have xcoff support

Fixed error
```
Command Output (stderr):
--
fatal error: error in backend: Objective-C support is unimplemented for object file format
```
Source code in `clang/lib/CodeGen/CGObjCMac.cpp:5080`

```
  case llvm::Triple::Wasm:
  case llvm::Triple::GOFF:
  case llvm::Triple::SPIRV:
  case llvm::Triple::XCOFF:
  case llvm::Triple::DXContainer:
    llvm::report_fatal_error(
        "Objective-C support is unimplemented for object file format");
  }

```

Reviewed By: hubert.reinterpretcast

Differential Revision: https://reviews.llvm.org/D135848