tools: disable ObjC for wasm in SILFunctionExtractor (#31920)
Currently, `clang` doesn't support Objective-C with the WebAssembly object format. Because of this, `sil-function-extractor` tool crashes in [Clang's `CGObjCCommonMac::GetSectionName` function](https://github.com/apple/llvm-project/blob/c3e5ae3fdebb67d936aeec2b04b7d2b6a784f69e/clang/lib/CodeGen/CGObjCMac.cpp#L5065-L5084). Since Swift doesn't provide Objective-C interop for WebAssembly, it would make sense to disable it explicitly. `sil-function-extractor` is used in the test suite, so this PR is required for those tests to proceed when testing the WebAssembly toolchain and SDK.
Related to SR-9307.
Co-authored-by: Saleem Abdulrasool <compnerd@compnerd.org>
