RFR: 8283929: GHA: Add RISC-V build config [v3]

Tue Sep 6 13:27:01 UTC 2022

> It adds CI for cross-compiling to linux-riscv64. It requires to use Ubuntu repositories for the debootstrap image because Debian doesn't have riscv64 packages on https://httpredir.debian.org/debian/. We can follow up on this change with switching to http://ports.ubuntu.com/ubuntu-ports for all cross-compiled architectures.
> 
> This change also does not require nor blocks switching to Ubuntu 22.04.
> 
> From talking with @shipilev, this replaces https://github.com/openjdk/jdk/pull/10086.

Ludovic Henry has updated the pull request incrementally with one additional commit since the last revision:

  Use Debian ports repository for riscv64

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/10168/files
  - new: https://git.openjdk.org/jdk/pull/10168/files/3be1706c..3a8bf39b

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=10168&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=10168&range=01-02

  Stats: 29 lines in 1 file changed: 3 ins; 6 del; 20 mod
  Patch: https://git.openjdk.org/jdk/pull/10168.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10168/head:pull/10168

PR: https://git.openjdk.org/jdk/pull/10168