RFR: 8297851: Add devkit for RISC-V [v2]

[Magnus Ihse Bursie]

> We should add devkit support for linux/riscv64.

Magnus Ihse Bursie has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains two additional commits since the last revision:

 - Merge branch 'master' into riscv-devkit
 - 8297851: Add devkit for RISC-V

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/11432/files
  - new: https://git.openjdk.org/jdk/pull/11432/files/984358b3..faf7988e

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=11432&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=11432&range=00-01

  Stats: 111920 lines in 2533 files changed: 56958 ins; 42193 del; 12769 mod
  Patch: https://git.openjdk.org/jdk/pull/11432.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11432/head:pull/11432

PR: https://git.openjdk.org/jdk/pull/11432