Buckify tokenizers (#8408)

Summary:
Pull Request resolved: #8408

X-link: pytorch-labs/tokenizers#17

So that it can be used by ET internally

Reviewed By: jackzhxng

Differential Revision: D69509028

Author: larryliu0820

shim/xplat/executorch/build/env_interface.bzl

@@ -39,9 +39,12 @@ _EXTERNAL_DEPS = {
     "gtest_aten": "//third-party:gtest_aten",
     "libtorch": "//third-party:libtorch",
     "libtorch_python": "//third-party:libtorch_python",
+    # Huggingface Tokenizer
+    "nlohmann_json": [], # Intentionally not supporting OSS buck build HF tokenizer.
     "prettytable": "//third-party:prettytable",
     "pybind11": "//third-party:pybind11",
     "re2": "//extension/llm/third-party:re2",
+    "sentencepiece": [], # Intentionally not supporting OSS buck build of sentencepiece.
     "sentencepiece-py": [],
     # Core C++ PyTorch functionality like Tensor and ScalarType.
     "torch-core-cpp": "//third-party:libtorch",