Target 需要语言方言“CXX17”（带有编译器扩展），但 CMake 不知道用于启用它的编译标志

Question

新手上路，请多包涵

所以我一直在尝试将 <filesystem> 包含到我的项目中，这似乎是一个比我想象的更大的问题。 <filesystem> 应该是 c++17 的一部分，我需要将该定义添加到我的 CMakeList 中。

我的根 CmakeLists 如下所示：

 MESSAGE(“In src CMAKELIST”)

#
# Build everything in include/ directory
add_subdirectory(include)
#

#set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)
#set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)
set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR})

set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

## Main executable target
add_executable(cmakeDemo main.cpp)

# These libraries get built in include/*/, CMake will auto-set required
# compiler flags and include paths from their definitions
target_link_libraries(cmakeDemo record ${portaudio})
target_link_libraries(cmakeDemo database)
target_link_libraries(cmakeDemo match)
target_link_libraries(cmakeDemo spectogram)

我在其中添加了 c++17 定义，但是当我编译我的系统时，我得到了这个错误：

  make
“InsrcCMAKELIST”
“InincludeCMAKELIST”
“IndatabaseCMAKELIST”
“InmatchCMAKELIST”
“InrecordCMAKELIST”
“InspectogramCMAKELIST”
/home/lamda/soundcloud/src/include/spectogram/base/base.h
“outspectogramCMAKELIST”
-- Configuring done
CMake Error in src/CMakeLists.txt:
  Target "cmakeDemo" requires the language dialect "CXX17" (with compiler
  extensions), but CMake does not know the compile flags to use to enable it.

-- Generating done
-- Build files have been written to: /home/lamda/soundcloud/build
make: *** [cmake_check_build_system] Error 1

但不知何故不愿意使用c++17，所以我可以使用 filesystem 库？为什么？