如果一个项目创建了一个add_library的库，那么使用target名称链接到该库。在这种情况下不要使用库文件。
根据cryptopp项目的CMakeLists.txt，库目标的名称是cryptopp-shared，所以只需链接它：

target_link_libraries(hmmenc-client PRIVATE cryptopp-shared)

详细说明

您将可执行文件与生成的库文件链接。所以你需要确保，这个文件的生成是在链接你的可执行文件之前执行的。
在CMake中，操作之间的顺序由目标之间的依赖关系指定。因此，您的可执行文件应该被指定为dependent从库作为目标。在CMake中，目标之间的依赖关系由add_dependencies()命令指定。
然而，CMake提供了一种方便的方法，可以同时链接到库并指定依赖项。当您链接到库target（由add_library创建）时：

1. CMake知道哪个库文件对应于该库目标，因此它使用该文件进行实际链接。
2. CMake自动调整可执行目标和库目标之间的依赖关系。

**更新：**如果使用CRYPTOPP_8_6_0以上版本的cryptopp-cmake，该流程需要更新，将无法正常工作。

我最终在Linux下使用了这个设置：

# Include usage of external projects
include(FetchContent)

############################################################################################
# Get the CryptoPP CMakeLists.txt File for CryptoPP Package GIT_TAG Must be the Same
############################################################################################
message(CHECK_START "Fetching CryptoPP-CMAKE")
set(CRYPTOPP_CMAKE "cryptopp-cmake")
set(CRYPTOPP_GIT_TAG "CRYPTOPP_8_2_0")
FetchContent_Declare(
        ${CRYPTOPP_CMAKE}
        GIT_REPOSITORY  https://github.com/noloader/cryptopp-cmake
        GIT_TAG         ${CRYPTOPP_GIT_TAG}
)

FetchContent_GetProperties(${CRYPTOPP_CMAKE})
if(NOT ${CRYPTOPP_CMAKE}_POPULATED)
    FetchContent_Populate(${CRYPTOPP_CMAKE})
endif()

############################################################################################
# Get the CryptoPP Package
############################################################################################
message(CHECK_START "Fetching CryptoPP")
set(CRYPTOPP "cryptopp")
FetchContent_Declare(
        ${CRYPTOPP}
        GIT_REPOSITORY  https://github.com/weidai11/cryptopp
        GIT_TAG         ${CRYPTOPP_GIT_TAG}
)

FetchContent_GetProperties(${CRYPTOPP})
if(NOT ${CRYPTOPP}_POPULATED)
    FetchContent_Populate(${CRYPTOPP})
    # !!! IMPORTANT !!!
    # Copy the CMakeLists.txt file from https://github.com/noloader/cryptopp-cmake with same TAG CRYPTOPP repository into ${${CRYPTOPP}_SOURCE_DIR}
    # before using add_subdirectory(), include_directories() and set(CRYPTOPP_LIB....) commands, until the a proper COPY command was implemented.
    file(COPY ${${CRYPTOPP_CMAKE}_SOURCE_DIR}/CMakeLists.txt DESTINATION ${${CRYPTOPP}_SOURCE_DIR})
    add_subdirectory(${${CRYPTOPP}_SOURCE_DIR} ${${CRYPTOPP}_BINARY_DIR})
endif()
include_directories(${${CRYPTOPP}_SOURCE_DIR})

# Set Cryptopp library properties every time after the first population
if(${CRYPTOPP}_POPULATED)
    # Build shared or static library
    set(BUILD_SHARED_CRYPTOPP_OLD ${BUILD_SHARED})
    set(BUILD_SHARED ON CACHE INTERNAL "Build CryptoPP SHARED libraries")
    message("Build CryptoPP shared lib is set to: ${BUILD_SHARED}")
    if(${BUILD_SHARED} STREQUAL "ON")
        set(CRYPTOPP "cryptopp-shared")
        else ()
            set(CRYPTOPP "cryptopp-static")
    endif()
    set(BUILD_SHARED ${BUILD_SHARED_CRYPTOPP_OLD} CACHE BOOL "Type of libraries to build" FORCE)
endif()

# Link the project libraries to the executable
target_link_libraries(my_project PRIVATE
        ${CRYPTOPP}
)