[riscv-port-jdk11u:riscv-port] RFR: 8316645: RISC-V: Remove dependency on libatomic by adding cmpxchg 1b [v2]

[Robbin Ehn]

> For CI builds it helps to remove this.
> [8317335](https://bugs.openjdk.org/browse/JDK-8317335) is not needed as there is no gtest for atomic in 11.

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

  Fix old compiler

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

Changes:
  - all: https://git.openjdk.org/riscv-port-jdk11u/pull/10/files
  - new: https://git.openjdk.org/riscv-port-jdk11u/pull/10/files/3f2651e4..a01cf4f8

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=riscv-port-jdk11u&pr=10&range=01
 - incr: https://webrevs.openjdk.org/?repo=riscv-port-jdk11u&pr=10&range=00-01

  Stats: 4 lines in 1 file changed: 2 ins; 1 del; 1 mod
  Patch: https://git.openjdk.org/riscv-port-jdk11u/pull/10.diff
  Fetch: git fetch https://git.openjdk.org/riscv-port-jdk11u.git pull/10/head:pull/10

PR: https://git.openjdk.org/riscv-port-jdk11u/pull/10