RFR: 8309001: Allow building JavaFX on Linux/riscv64 [v3]

[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 incrementally with one additional commit since the last revision:

  8309001: Allow building JavaFX on Linux/riscv64
  
  Reviewed-by: kcr, jvos

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Changes:
  - all: https://git.openjdk.org/jfx/pull/1146/files
  - new: https://git.openjdk.org/jfx/pull/1146/files/040d1d71..74bed4e3

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=1146&range=02
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=1146&range=01-02

  Stats: 0 lines in 0 files changed: 0 ins; 0 del; 0 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