protect cmakelist for extension under NEURON_BUFFER_ALLOCATOR_LIB flag

Author: cmodi-meta

extension/android/CMakeLists.txt

@@ -156,25 +156,27 @@ if(EXECUTORCH_BUILD_LLAMA_JNI)
     ${CMAKE_CURRENT_BINARY_DIR}/../../examples/models/llama2/runner
   )
 
-    target_sources(
-    executorch_jni PRIVATE
-    ${EXECUTORCH_ROOT}/examples/mediatek/executor_runner/mtk_llama_runner.cpp
-    ${EXECUTORCH_ROOT}/examples/mediatek/executor_runner/llama_runner/LlamaModelChunk.cpp
-    ${EXECUTORCH_ROOT}/examples/mediatek/executor_runner/llama_runner/LlamaRuntime.cpp
-    ${EXECUTORCH_ROOT}/examples/mediatek/executor_runner/llama_runner/ModelChunk.cpp
-    ${EXECUTORCH_ROOT}/examples/mediatek/executor_runner/llama_runner/MultiModelLoader.cpp
-    ${EXECUTORCH_ROOT}/examples/mediatek/executor_runner/llama_runner/llm_helper/mask_builder.cpp
-    ${EXECUTORCH_ROOT}/examples/mediatek/executor_runner/llama_runner/llm_helper/rotary_embedding.cpp
-    ${EXECUTORCH_ROOT}/examples/mediatek/executor_runner/llama_runner/llm_helper/token_embedding.cpp
-  )
-  target_include_directories(
-    executorch_jni PRIVATE
-    ${EXECUTORCH_ROOT}/examples/mediatek/executor_runner/
-    ${EXECUTORCH_ROOT}/examples/mediatek/executor_runner/llama_runner
-  )
-  ADD_LIBRARY(libneuron_buffer_allocator SHARED IMPORTED)
-  SET_PROPERTY(TARGET libneuron_buffer_allocator PROPERTY IMPORTED_LOCATION ${NEURON_BUFFER_ALLOCATOR_LIB})
-  list(APPEND link_libraries neuron_backend libneuron_buffer_allocator)
+  if(NEURON_BUFFER_ALLOCATOR_LIB)
+      target_sources(
+      executorch_jni PRIVATE
+      ${EXECUTORCH_ROOT}/examples/mediatek/executor_runner/mtk_llama_runner.cpp
+      ${EXECUTORCH_ROOT}/examples/mediatek/executor_runner/llama_runner/LlamaModelChunk.cpp
+      ${EXECUTORCH_ROOT}/examples/mediatek/executor_runner/llama_runner/LlamaRuntime.cpp
+      ${EXECUTORCH_ROOT}/examples/mediatek/executor_runner/llama_runner/ModelChunk.cpp
+      ${EXECUTORCH_ROOT}/examples/mediatek/executor_runner/llama_runner/MultiModelLoader.cpp
+      ${EXECUTORCH_ROOT}/examples/mediatek/executor_runner/llama_runner/llm_helper/mask_builder.cpp
+      ${EXECUTORCH_ROOT}/examples/mediatek/executor_runner/llama_runner/llm_helper/rotary_embedding.cpp
+      ${EXECUTORCH_ROOT}/examples/mediatek/executor_runner/llama_runner/llm_helper/token_embedding.cpp
+    )
+    target_include_directories(
+      executorch_jni PRIVATE
+      ${EXECUTORCH_ROOT}/examples/mediatek/executor_runner/
+      ${EXECUTORCH_ROOT}/examples/mediatek/executor_runner/llama_runner
+    )
+    ADD_LIBRARY(libneuron_buffer_allocator SHARED IMPORTED)
+    SET_PROPERTY(TARGET libneuron_buffer_allocator PROPERTY IMPORTED_LOCATION ${NEURON_BUFFER_ALLOCATOR_LIB})
+    list(APPEND link_libraries neuron_backend libneuron_buffer_allocator)
+  endif()
 endif()
 
 target_include_directories(