RFR: 8273927: Enable hsdis for riscv64

[Aleksey Shipilev]

Currently compiled `hsdis-riscv64.so` binary complains:


hsdis: bad native mach=architecture not set in Makefile!; please port hsdis to this platform


It seems to be as simple as point to the right BFD arch.

Additional testing:
 - [x] Linux RISC-V port, `-XX:+PrintAssembly` works

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Commit messages:
 - Fix

Changes: https://git.openjdk.java.net/jdk/pull/5558/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5558&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8273927
  Stats: 3 lines in 1 file changed: 3 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5558.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5558/head:pull/5558

PR: https://git.openjdk.java.net/jdk/pull/5558