[BUILD] Download pybind11 in setup.py (#703) (#797)

Cherry-picks #703 and resolves conflicts

Co-authored-by: Shintaro Iwasaki <siwasaki@fb.com>

CMakeLists.txt

@@ -5,11 +5,6 @@ set(CMAKE_CXX_STANDARD 17)
 
 set(CMAKE_INCLUDE_CURRENT_DIR ON)
 
-if(NOT TRITON_LLVM_BUILD_DIR)
-    set(TRITON_LLVM_BUILD_DIR ${CMAKE_BINARY_DIR})
-endif()
-
-
 project(triton)
 include(CTest)
 if(NOT WIN32)
@@ -33,6 +28,9 @@ endif()
 # Compiler flags
 include_directories(${CMAKE_CURRENT_SOURCE_DIR}/include)
 
+# Third-party
+include_directories(${PYBIND11_INCLUDE_DIR})
+
 if(WIN32)
     SET(BUILD_SHARED_LIBS OFF)
     include_directories(${CMAKE_CURRENT_SOURCE_DIR}/deps/dlfcn-win32/src)