RFR: 8309001: Add Linux/riscv64 support to WebKit [v2]

[Eric Long]

> RISC-V is a new free and open-source ISA that is being widely adopted in the recent years. Currently WebKit is ready for riscv64, and only minor changes is needed to support the platform.

Eric Long has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains one commit:

  8309001: Add Linux/riscv64 support

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Changes: https://git.openjdk.org/jfx/pull/1146/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1146&range=01
  Stats: 6 lines in 1 file changed: 5 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jfx/pull/1146.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1146/head:pull/1146

PR: https://git.openjdk.org/jfx/pull/1146