RFR: 7902912: Update IntelliJ Plugin build Readme

[Maurizio Cimadamore]

On Fri, 30 Apr 2021 08:58:00 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

> Hi, may I have reviews for this small documentation fix please? I am not a CODETOOLS committer so I may need someone to sponsor this fix.
> 
> Since I just built the intellij plugin in 2020.3, I stumbled about a couple of ambiguous infos which are not immediately clear to outsiders.
> 
> -> some UI features changed in Intellij
> -> Clarified the meaning of JTREG_HOME
> -> One thing I was not sure about was the required SDK level to build the plugin. The documentation says "Any JDK 8 is fine" which I took as "JDK8 is required" - proceeded to download JDK 8 but then I was unable to choose this JDK as a SDK for the IDEA JDK. It was, however, happy with a JDK 15 I gave it, and proceeded to build the plugin without any issues. Therefore I changed the sentence to "Any JDK 8++ is a fine choice".

Looks great - thanks! I've added a small suggestion.

plugins/idea/README.md line 40:

> 38: * When the IDE project for the plugin is first opened, IntelliJ will complain about the lack of a path variable called `JTREG_HOME`. Please follow the IDE instructions, and set this path variable to point to the root of your jtreg build output or your jtreg installation (`JTREG_HOME/libs/javatest.jar` must exist). The setting can also be found in under `Settings -> Appearance and Behavior -> Path Variables`. This step is required as the project depends on some of the jtreg libraries.
> 39: 
> 40: * You need to create an Intellij SDK and name it `IDEA JDK` for the project to work correctly. To create a new SDK, click on `File -> Project Structure`. When the dialog opens, click on the `SDKs` entry in the left pane, and add a new SDK (by clicking on the *plus* icon). The SDK we want to create is an 'IntelliJ Platform Plugin SDK'. Once the new SDK type has been selected, you will have to tell IntelliJ what's the SDK path - you will see that IntelliJ will already point to the folder containing your IntelliJ installation - that is a fine choice. Rename it to `IDEA JDK`. Secondly, you will have to tell IntelliJ which JDK to use together with the plugin SDK. Any JDK 8++ is a fine choice here.

Suggestion:

* You need to create an Intellij SDK and name it `IDEA JDK` for the project to work correctly. To create a new SDK, click on `File -> Project Structure`. When the dialog opens, click on the `SDKs` entry in the left pane, and add a new SDK (by clicking on the *plus* icon). The SDK we want to create is an 'IntelliJ Platform Plugin SDK'. Once the new SDK type has been selected, you will have to tell IntelliJ what's the SDK path - you will see that IntelliJ will already point to the folder containing your IntelliJ installation - that is a fine choice. Rename it to `IDEA JDK`. Secondly, you will have to tell IntelliJ which JDK to use together with the plugin SDK. Any JDK 8 (or greater) is a fine choice here.

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Marked as reviewed by mcimadamore (Committer).

PR: https://git.openjdk.java.net/jtreg/pull/8