Patch cmake build on mac

Summary:
1. bump cmake minimum version to 3.19 so that we can use `add_library INTERFACE {sources}`
2. add `-force_load` for `clang_kernel_link_options` so it can force load kernel library.

Reviewed By: kimishpatel, dbort

Differential Revision: D48328846

fbshipit-source-id: 1713619a426e23e7938a2872e64189fe53f2e333

Author: larryliu0820

CMakeLists.txt

@@ -40,7 +40,7 @@
 # It should also be cmake-lint clean.
 #
 
-cmake_minimum_required(VERSION 3.13)
+cmake_minimum_required(VERSION 3.19)
 project(executorch)
 include(build/Utils.cmake)
 
@@ -152,7 +152,7 @@ add_custom_command(
   COMMENT "Generating program_schema headers"
   VERBATIM)
 
-add_library(program_schema ${_program_schema__outputs})
+add_library(program_schema INTERFACE ${_program_schema__outputs})
 set_target_properties(program_schema PROPERTIES LINKER_LANGUAGE CXX)
 target_include_directories(
   program_schema

build/Utils.cmake

@@ -30,7 +30,7 @@ function(clang_kernel_link_options target_name)
         # for targets that depend on this library; once because CMake will add
         # it, and once because it's in this list of args. See if there's a way
         # to avoid that.
-        -Wl,$<TARGET_FILE:${target_name}>
+        -Wl,-force_load,$<TARGET_FILE:${target_name}>
     )
 endfunction()
 

docs/website/docs/tutorials/cmake_build_system.md

@@ -41,7 +41,7 @@ useful to embedded systems users.
      install` inside your conda environment if you created one during AOT Setup
      (see [Setting up
      Executorch](00_setting_up_executorch.md#aot-setup-open-on-google-colab)).
-1. Install CMake version 3.13 or later
+1. Install CMake version 3.19 or later
 
 ## Configure the CMake build
 

examples/custom_ops/CMakeLists.txt

@@ -13,7 +13,7 @@
 # both binding wrapper and the implementation source file. This library can be
 # linked into Executorch binary (`executor_runner` in this example) and it is
 # ready to run models containing that custom op.
-cmake_minimum_required(VERSION 3.13)
+cmake_minimum_required(VERSION 3.19)
 
 set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
 if(NOT CMAKE_CXX_STANDARD)