8283929: GHA: Add RISC-V build config

[gnu-andrew]

JDK-8199138 was added to 11u back in 2021 to allow Zero to support RISC-V, but it wasn't added to the GHA cross compile testing so we have no idea if it actually builds or gets broken by patches. This came to my intention when looking at the proposal to add RISC-V Zero support to 8u

---

• I confirm that I make this contribution in accordance with the OpenJDK Interim AI Policy.

---

Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• JDK-8283929 needs maintainer approval

Issue

• JDK-8283929: GHA: Add RISC-V build config (Enhancement - P4)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk11u-dev.git pull/3205/head:pull/3205
$ git checkout pull/3205

Update a local copy of the PR:
$ git checkout pull/3205
$ git pull https://git.openjdk.org/jdk11u-dev.git pull/3205/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 3205

View PR using the GUI difftool:
$ git pr show -t 3205

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk11u-dev/pull/3205.diff

[bridgekeeper]

👋 Welcome back andrew! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[openjdk]

❗ This change is not yet ready to be integrated.
See the Progress checklist in the description for automated requirements.

[openjdk]

This backport pull request has now been updated with issue from the original commit.

[gnu-andrew]

Looks like this will need the bump to trixie first.

[openjdk-notifier]

The parent pull request that this pull request depends on has now been integrated and the target branch of this pull request has been updated. This means that changes from the dependent pull request can start to show up as belonging to this pull request, which may be confusing for reviewers. To remedy this situation, simply merge the latest changes from the new target branch into this pull request by running commands similar to these in the local repository for your personal fork:

git checkout riscv-gha
git fetch https://git.openjdk.org/jdk11u-dev.git master
git merge FETCH_HEAD
# if there are conflicts, follow the instructions given by git merge
git commit -m "Merge master"
git push