Add sentencepiece tokenizer support to llm runner (#85)

Summary:
Pull Request resolved: #85

Fixes pytorch/executorch#11618

Add sentencepiece tokenizer support

X-link: pytorch/executorch#11645

Differential Revision: D76789606

Pulled By: larryliu0820

Author: larryliu0820

targets.bzl

@@ -101,7 +101,7 @@ def define_common_targets():
             "@EXECUTORCH_CLIENTS",
             "//pytorch/tokenizers/...",
         ],
-        external_deps = [
+        exported_external_deps = [
             "sentencepiece",
             "abseil-cpp",
         ],