要在cmake中链接库（共享/静态），可以使用target_link_libraries命令：

target_link_libraries(<target> ... <item>... ...)

根据文件：
<target>必须已由add_executable()或add_library()之类的命令创建
因此，首先我们需要找到SDL库，为此，我们将使用以下命令：

find_package(SDL2 REQUIRED)

要使它的include目录对您可用，请使用以下命令：

include_directories(${SDL2_INCLUDE_DIRS})

最后，要链接SDL2，您需要：

target_link_libraries(${PROJECT_NAME} ${SDL2_LIBRARIES})

或备选：

target_link_libraries(${PROJECT_NAME} PRIVATE SDL2::SDL2)

PRIVATE，意味着${PROJECT_NAME}在其实现中使用SDL2，但是SDL2不在${PROJECT_NAME}的公共API的任何部分中使用。
这里的${PROJECT_NAME}是<target>，后面的所有名称都是库的名称。

最终结果

# Set the minimum version of CMake that can be used
# To find the cmake version run
# $ cmake --version
cmake_minimum_required(VERSION 3.5)

# Set the project name
project (sdl)

find_package(SDL2 REQUIRED)

# Create a sources variable with a link to all cpp files to compile
set(SOURCES
    src/main.cpp
)

# Add an executable with the above sources
add_executable(${PROJECT_NAME} ${SOURCES})

target_link_libraries(sdl ${SDL2_LIBRARIES})

# Set the directories that should be included in the build command for this target
include_directories(SDL2Test ${SDL2_INCLUDE_DIRS})

参考文献：

1. https://cmake.org/cmake/help/latest/command
2. https://cmake.org/pipermail/cmake/2016-May/063400.html

***编辑***已添加完整的CMAKE

# Set the minimum version of CMake that can be used
# To find the cmake version run
# $ cmake --version
cmake_minimum_required(VERSION 3.5)

# Set the project name
project (sdl)

# Create a sources variable with a link to all cpp files to compile
set(SOURCES
    src/main.cpp
)

 target_include_directories(sdl
        PRIVATE 
            ${PROJECT_SOURCE_DIR}/inc
    )

# Add an executable with the above sources

link_directories(path_to_lib)
    add_executable(${PROJECT_NAME} ${SOURCES})

# Set the directories that should be included in the build command for this target
# when running g++ these will be included as -I/directory/path/

 target_link_libraries((${PROJECT_NAME} SDL2 SDL2_mixer SDL2_image SDL2_ttf)