[riscv-port-jdk17u:riscv-port] RFR: 8296771: RISC-V: C2: assert(false) failed: bad AD file

[Gui Cao]

Please review this backport to riscv-port-jdk17u.
Backport of [JDK-8296771](https://bugs.openjdk.org/browse/JDK-8296771). Applies cleanly.

Testing:
- compiler/runtime/TestConstantsInError.java passed on qemu (fastdebug).
- Tier1 passed without new failure on unmacthed (release).

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Commit messages:
 - 8296771: RISC-V: C2: assert(false) failed: bad AD file

Changes: https://git.openjdk.org/riscv-port-jdk17u/pull/8/files
 Webrev: https://webrevs.openjdk.org/?repo=riscv-port-jdk17u&pr=8&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8296771
  Stats: 1 line in 1 file changed: 1 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/riscv-port-jdk17u/pull/8.diff
  Fetch: git fetch https://git.openjdk.org/riscv-port-jdk17u pull/8/head:pull/8

PR: https://git.openjdk.org/riscv-port-jdk17u/pull/8