docker build-FindSDL2.cmake
The error information is as follows，how to solve it？Thangk you！

CMake Error at Source/Tools/FEXConfig/CMakeLists.txt:7 (find_package):
  By not providing "FindSDL2.cmake" in CMAKE_MODULE_PATH this project has
  asked CMake to find a package configuration file provided by "SDL2", but
  CMake did not find one.

  Could not find a package configuration file provided by "SDL2" with any of
  the following names:

    SDL2Config.cmake
    sdl2-config.cmake

  Add the installation prefix of "SDL2" to CMAKE_PREFIX_PATH or set
  "SDL2_DIR" to a directory containing one of the above files.  If "SDL2"
  provides a separate development package or SDK, be sure it has been
  installed.