custom一词应该翻译成定制化比较合适，表示cmake提供了让用户添加定制化命令的手段。

该命令有两种格式，

1、用法1 添加一个伪目标用以执行某些命令

add_custom_command(OUTPUT output1 [output2 ...]
                   COMMAND command1 [ARGS] [args1...]
                   [COMMAND command2 [ARGS] [args2...] ...]
                   [MAIN_DEPENDENCY depend]
                   [DEPENDS [depends...]]
                   [BYPRODUCTS [files...]]
                   [IMPLICIT_DEPENDS <lang1> depend1
                                    [<lang2> depend2] ...]
                   [WORKING_DIRECTORY dir]
                   [COMMENT comment]
                   [DEPFILE depfile]
                   [JOB_POOL job_pool]
                   [VERBATIM] [APPEND] [USES_TERMINAL]
                   [COMMAND_EXPAND_LISTS])

该命令翻译成Makefile语法就是：

OUTPUT: MAIN_DEPENDENCY DEPENDS
        COMMAND