我尝试在pico-sdk中运行spp_counter. c示例。当我运行make时，我得到这个错误：

fatal error: btstack.h: No such file or directory
58 | #include "btstack.h"

代码来自the repository。CMakeLists.txt:

cmake_minimum_required(VERSION 3.13)

# initialize the SDK based on PICO_SDK_PATH
# Include build functions from Pico SDK
include($ENV{PICO_SDK_PATH}/external/pico_sdk_import.cmake)

project(my_project)

# initialize the Raspberry Pi Pico SDK
set(PICO_BOARD pico_w)

pico_sdk_init()

# rest of your project
add_executable(test
    test.c
)

# Add pico_stdlib library which aggregates commonly used features
target_link_libraries(test pico_stdlib)

# create map/bin/hex/uf2 file in addition to ELF.
pico_add_extra_outputs(test)

我不知道我错过了什么。