构建源支持jdk21项目

[xggz]

java21 是最新的lts版本，希望支持一下

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Title: The build source supports the jdk21 project

java21 is the latest lts version, I hope to support it

[yangkaa]

预计在 5.18 版本中推出支持用户自行上传语言包的功能。到时候即可自行升级 JDK 版本、各类源码构建版本。当前你应该可以通过自定义 OpenJDK ，设置你需要的JDK版本。

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It is expected that the function to support users to upload language packs will be launched in version 5.18. At that time, you can upgrade the JDK version and various source code build versions by yourself. Currently you should be able to set the JDK version you need by customizing OpenJDK.