[jdk21] RFR: 8310656: RISC-V: __builtin___clear_cache can fail silently. [v2]

[Robbin Ehn]

> Hi all,
> 
> This pull request contains a backport of commit [faf1b822](https://github.com/openjdk/jdk/commit/faf1b822d03b726413d77a2b247dfbbf4db7d57e) from the [openjdk/jdk](https://git.openjdk.org/jdk) repository.
> 
> The commit being backported was authored by Robbin Ehn on 2 Jul 2023 and was reviewed by Ludovic Henry, Thomas Stuefe and Fei Yang.
> 
> Thanks!

Robbin Ehn has updated the pull request incrementally with one additional commit since the last revision:

  Added missing global defines in jdk 21
  
  Signed-off-by: Robbin Ehn <rehn at rivosinc.com>

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

Changes:
  - all: https://git.openjdk.org/jdk21/pull/90/files
  - new: https://git.openjdk.org/jdk21/pull/90/files/be817c39..be7724a4

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk21&pr=90&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk21&pr=90&range=00-01

  Stats: 10 lines in 1 file changed: 10 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk21/pull/90.diff
  Fetch: git fetch https://git.openjdk.org/jdk21.git pull/90/head:pull/90

PR: https://git.openjdk.org/jdk21/pull/90