[riscv-port-jdk11u:riscv-port] RFR: 8328065: RISC-V: Add isolation for shared code changes

[Gui Cao]

Hi, We want to add isolation for shared code changes. 
1. To minimize the difference with jdk17u-dev upstream, the jdk17u-dev backport does isolate public code changes to avoid code changes to other architectures [1] 
2. riscv-port-jdk11u is missing the sparc architecture adaptation in the backport, this may affect the correctness of the sparc architecture.
### Test
- [x] Run tier1-3 tests on linux-x86 (release)
- [x] Run tier1-3 tests on linux-arm64 (release)
- [x] Run tier1-3 tests on on LicheePI 4A (release)

[1] https://github.com/yadongw/riscv-port-jdk17u/commit/6bc31f690036ebf7d0db55b1e2ef83b13b74fed3

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

Commit messages:
 - 8328065: RISC-V: Add isolation for shared code changes

Changes: https://git.openjdk.org/riscv-port-jdk11u/pull/11/files
  Webrev: https://webrevs.openjdk.org/?repo=riscv-port-jdk11u&pr=11&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8328065
  Stats: 168 lines in 12 files changed: 126 ins; 16 del; 26 mod
  Patch: https://git.openjdk.org/riscv-port-jdk11u/pull/11.diff
  Fetch: git fetch https://git.openjdk.org/riscv-port-jdk11u.git pull/11/head:pull/11

PR: https://git.openjdk.org/riscv-port-jdk11u/pull/11