esp32, esp32s2: move startup code into esp_system

components/esp32/CMakeLists.txt

@@ -15,7 +15,6 @@ else()
         "cache_err_int.c"
         "cache_sram_mmu.c"
         "clk.c"
-        "cpu_start.c"
         "crosscore_int.c"
         "dport_access.c"
         "esp_himem.c"
@@ -48,8 +47,6 @@ else()
 
     target_linker_script(${COMPONENT_LIB} INTERFACE "${CMAKE_CURRENT_BINARY_DIR}/esp32_out.ld")
 
-    # Rely on user code to define app_main
-    target_link_libraries(${COMPONENT_LIB} INTERFACE "-u app_main")
 
     if(CONFIG_SPIRAM_ALLOW_BSS_SEG_EXTERNAL_MEMORY)
         # This has to be linked before esp32.project.ld