鉴于以下项目结构：

.
└── library/
    ├── CMakeLists.txt
    ├── include/
    │   └── class1.hpp
    ├── src/
    │   └── class1.cpp
    ├── build/
    │   ├── _deps/
    │   │   └── fmt-build
    │   └── sample/
    │       └── app_using_library.exe
    └── sample/
        ├── CMakeLists.txt
        └── main.cpp

程式库的CMakeLists.txt：

project(library)

include(FetchContent)

FetchContent_Declare(
        fmt
        URL https://github.com/fmtlib/fmt/releases/download/9.1.0/fmt-9.1.0.zip
)
FetchContent_MakeAvailable(fmt)

add_library(library STATIC 
  "src/class1.cpp" 
  "include/class1.hpp" 
target_include_directories(library PUBLIC include)
target_link_libraries(library PRIVATE fmt::fmt)

应用程序使用库的CMakeLists.txt文件：

project(app_using_library)
add_executable(app_using_library main.cpp)
target_link_libraries(app_using_library PRIVATE library)

class1.hpp:
#include "fmt/core.h" // cannot open source file "fmt/core.h"
class1.cpp:
#include "fmt/core.h" // works fine
在构建library和app_using_library时，fmt头文件可以包含在class1.cpp中，而不能包含在class1.hpp中，是否有可能的原因或解释？在仅构建library时，include在头文件中工作正常
编译器无法在“class1.hpp”中找到fmt头文件，但可以在“class1.cpp”中找到它们。
全错误：

FAILED: sample/CMakeFiles/app_using_library.dir/main.cpp.obj 
  C:\msys64\mingw64\bin\g++.exe  -ID:/Programming/cpp/library/include -g -std=gnu++20 -MD -MT sample/CMakeFiles/app_using_library.dir/main.cpp.obj -MF sample\CMakeFiles\app_using_library.dir\main.cpp.obj.d -o sample/CMakeFiles/app_using_library.dir/main.cpp.obj -c D:/Programming/cpp/library/sample/main.cpp
  In file included from D:/Programming/cpp/library/sample/main.cpp:2:
  D:/Programming/cpp/library/include/class1.hpp:4:10: fatal error: fmt/core.h: No such file or directory
      4 | #include "fmt/core.h"
        |          ^~~~~~~~~~~~
  compilation terminated.