这是我第一次cmake软件，按照官方给的命令步骤，发生了以下错误

pcman@pcman-PC:~$ git clone https://invent.kde.org/graphics/okular.git

正克隆到 'okular'...

remote: Enumerating objects: 81214, done.

remote: Counting objects: 100% (1950/1950), done.

remote: Compressing objects: 100% (737/737), done.

remote: Total 81214 (delta 1323), reused 1814 (delta 1208), pack-reused 79264

接收对象中: 100% (81214/81214), 21.71 MiB | 2.88 MiB/s, 完成.

处理 delta 中: 100% (65995/65995), 完成.

pcman@pcman-PC:~$ cd okular

pcman@pcman-PC:~/okular$ mkdir build

pcman@pcman-PC:~/okular$ cd build

pcman@pcman-PC:~/okular/build$ cmake -DCMAKE_INSTALL_PREFIX=/path/to/your/install/dir ..

-- The C compiler identification is GNU 8.3.0

-- The CXX compiler identification is GNU 8.3.0

-- Detecting C compiler ABI info

-- Detecting C compiler ABI info - done

-- Check for working C compiler: /usr/bin/cc - skipped

-- Detecting C compile features

-- Detecting C compile features - done

-- Detecting CXX compiler ABI info

-- Detecting CXX compiler ABI info - done

-- Check for working CXX compiler: /usr/bin/c++ - skipped

-- Detecting CXX compile features

-- Detecting CXX compile features - done

CMake Error at CMakeLists.txt:31 (find_package):

  Could not find a package configuration file provided by "ECM" (requested

  version 5.68.0) with any of the following names:

 

    ECMConfig.cmake

    ecm-config.cmake

 

  Add the installation prefix of "ECM" to CMAKE_PREFIX_PATH or set "ECM_DIR"

  to a directory containing one of the above files.  If "ECM" provides a

  separate development package or SDK, be sure it has been installed.

 

 

-- Configuring incomplete, errors occurred!

See also "/home/pcman/okular/build/CMakeFiles/CMakeOutput.log".