Update on "[ExecuTorch] Proof-of-concept: use c10/macros in ExecuTorch"

Step 0 for code sharing: can we use c10 Macros?

This needs a guardrail to prevent breaking the ExecuTorch core
requirements before we can ship it. What's our current guard against
accidentally including streams/heap allocation/etc. in core at runtime?

Differential Revision: [D65241695](https://our.internmc.facebook.com/intern/diff/D65241695/)

[ghstack-poisoned]

Author: swolchok

CMakeLists.txt

@@ -324,7 +324,9 @@ message(STATUS "Using python executable '${PYTHON_EXECUTABLE}'")
 set(_common_compile_options -Wno-deprecated-declarations -fPIC)
 
 # Let files say "include <executorch/path/to/header.h>".
-set(_common_include_directories ${CMAKE_CURRENT_SOURCE_DIR}/..)
+find_package(Torch CONFIG REQUIRED)
+
+set(_common_include_directories ${CMAKE_CURRENT_SOURCE_DIR}/.. ${TORCH_INCLUDE_DIRS})
 
 #
 # The `_<target>_srcs` lists are defined by including ${EXECUTORCH_SRCS_FILE}.
@@ -507,9 +509,6 @@ endif()
 target_include_directories(
   executorch_core PUBLIC ${_common_include_directories}
 )
-target_include_directories(
-  executorch_core INTERFACE ${TORCH_INCLUDE_DIRS}
-)
 target_compile_options(executorch_core PUBLIC ${_common_compile_options})
 if(MAX_KERNEL_NUM)
   target_compile_definitions(
@@ -671,8 +670,6 @@ if(EXECUTORCH_BUILD_PTHREADPOOL
   add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/extension/threadpool)
 endif()
 
-find_package(Torch CONFIG REQUIRED)
-
 if(EXECUTORCH_BUILD_PYBIND)
   add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/third-party/pybind11)