[mlgo] Remove TENSORFLOW_C_LIB_PATH

[kazu]

Summary

We use LLVM_HAVE_TFLITE as the key to enable the MLGO bits. We do not
use the "else" clause.

llvm/CMakeLists.txt

 
 if(LLVM_INCLUDE_TESTS)
   include(GetErrcMessages)
   get_errc_messages(LLVM_LIT_ERRC_MESSAGES)
 endif()
 
 # For up-to-date instructions for installing the TFLite dependency, refer to
 # the bot setup script: https://github.com/google/ml-compiler-opt/blob/main/buildbot/buildbot_init.sh
-set(TENSORFLOW_C_LIB_PATH "" CACHE PATH "Path to TensorFlow C library install")
 set(LLVM_HAVE_TFLITE "" CACHE BOOL "Use tflite")
 if (LLVM_HAVE_TFLITE)
   find_package(protobuf REQUIRED)
   find_package(tensorflow-lite REQUIRED)
   set(LLVM_HAVE_TF_API "ON" CACHE BOOL "Full Tensorflow API available")
   set(LLVM_PROTOBUF_OUT_DIR ${CMAKE_LIBRARY_OUTPUT_DIRECTORY}/protobuf_gen)
   include_directories(${LLVM_PROTOBUF_OUT_DIR})
-elseif (TENSORFLOW_C_LIB_PATH)
-  find_library(tensorflow_c_api tensorflow PATHS ${TENSORFLOW_C_LIB_PATH}/lib NO_DEFAULT_PATH REQUIRED)
-  # Currently, the protobuf headers are distributed with the pip package that corresponds to the version
-  # of the C API library.
-  find_library(tensorflow_fx tensorflow_framework PATHS ${TENSORFLOW_C_LIB_PATH}/lib NO_DEFAULT_PATH REQUIRED)
-  set(LLVM_HAVE_TF_API "ON" CACHE BOOL "Full Tensorflow API available")
-  include_directories(${TENSORFLOW_C_LIB_PATH}/include)
-  if (NOT TF_PROTO_HEADERS)
-    message(STATUS "TF_PROTO_HEADERS not defined. Looking for tensorflow pip package.")
-    execute_process(COMMAND
-      ${Python3_EXECUTABLE} "-c" "import tensorflow as tf; import os; print(os.path.dirname(tf.__file__))"
-      OUTPUT_VARIABLE TF_PIP)
-    if ("${TF_PIP}" STREQUAL "")
-      message(FATAL ERROR "Tensorflow pip package is also required for 'development' mode (protobuf headers)")
-    endif()
-    string(STRIP ${TF_PIP} TF_PIP)
-    set(TF_PROTO_HEADERS "${TF_PIP}/include")
-  endif()
-  message(STATUS "Using Tensorflow headers under: ${TF_PROTO_HEADERS}")
-  include_directories(${TF_PROTO_HEADERS})
-  add_definitions("-DGOOGLE_PROTOBUF_NO_RTTI")
-  add_definitions("-D_GLIBCXX_USE_CXX11_ABI=0")
 endif()
 
 # For up-to-date instructions for installing the Tensorflow dependency, refer to
 # the bot setup script: https://github.com/google/ml-compiler-opt/blob/main/buildbot/buildbot_init.sh
 # Specifically, assuming python3 is installed:
 # python3 -m pip install --upgrade pip && python3 -m pip install --user tf_nightly==2.3.0.dev20200528
 # Then set TENSORFLOW_AOT_PATH to the package install - usually it's ~/.local/lib/python3.7/site-packages/tensorflow
 #