ExternalProject_add 执行所有步骤时间

ExternalProject_add executes all steps at build time, not at configuration time.

对于下载文件，您可以使用档案 （DOWNLOAD ...）命令。对于来自arhive的提取文件，只需使用适当的命令 execute_process 。

For download file you can use file(DOWNLOAD ...) command. For extract files from arhive just use execute_process with appropriate command.