[jdk17] RFR: 8259848: Interim javadoc build does not support platform links

[Hannes Wallnöfer]

On Wed, 7 Jul 2021 19:02:04 GMT, Erik Joelsson <erikj at openjdk.org> wrote:

> This patch adds copying of element-list files generated for jdk.javadoc to the interim langtools version of jdk.javadoc. I'm also refactoring the jdk.javadoc/Gendata.gmk file a bit to better adhere to current build infra standards as this was missed in the original review of this file. Rebuilding should now work better with the various clean targets and any problems with the generation tool will be captured in separate log files, along with the command lines.
> 
> @hns Can you verify that this solves the problem you reported?

I have verified that the interim JDK now contains the full list of element-list files with correct content, so this looks good.

The interim JDK is used to build the platform API docs with `make docs` and similar targets. The platform docs usually don't need the element list files for external links because the JDK libraries are themselves the subject of documentation. However, @jonathan-gibbons' doccheck tool uses the interim JDK to generate documentation for single modules, which is how we became aware of this problem. Jon has since changed his doccheck code to disable the platform links feature, it no longer requires these files.

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PR: https://git.openjdk.java.net/jdk17/pull/227