RFR: 8320050: Zero: Build failures due to duplicate definition of __sync_val_compare_and_swap_8

[Aleksey Shipilev]

See the sample build failure log in the bug. This provides a conservative fix that avoids the clash when `libatomic` provides us with the `__sync_val_compare_and_swap_8` implementation. The rest should be handled by moving to `__atomic` built-ins, see related issue.

For sanity, checked that all these build configurations are building fine:
  * server-fastdebug-aarch64-linux-gnu-10
  * server-fastdebug-arm-linux-gnueabihf-10
  * server-fastdebug-i686-linux-gnu-10
  * server-fastdebug-powerpc64le-linux-gnu-10
  * server-fastdebug-powerpc64-linux-gnu-10
  * server-fastdebug-riscv64-linux-gnu-10
  * server-fastdebug-s390x-linux-gnu-10
  * server-fastdebug-x86_64-linux-gnu-10
  * zero-fastdebug-aarch64-linux-gnu-10
  * zero-fastdebug-arm-linux-gnueabi-10
  * zero-fastdebug-arm-linux-gnueabihf-10
  * zero-fastdebug-i686-linux-gnu-10
  * zero-fastdebug-mips64el-linux-gnuabi64-10 
  * zero-fastdebug-powerpc64le-linux-gnu-10
  * zero-fastdebug-powerpc64-linux-gnu-10
  * zero-fastdebug-riscv64-linux-gnu-10
  * zero-fastdebug-s390x-linux-gnu-10
  * zero-fastdebug-sparc64-linux-gnu-10
  * zero-fastdebug-x86_64-linux-gnu-10

Configurations that are still broken due to undefined symbol:
  * zero-fastdebug-mipsel-linux-gnu-10
  * zero-fastdebug-m68k-linux-gnu-10
  * zero-fastdebug-powerpc-linux-gnu-10
  * zero-fastdebug-sh4-linux-gnu-10

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Commit messages:
 - Fix

Changes: https://git.openjdk.org/jdk/pull/16651/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16651&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8320050
  Stats: 4 lines in 2 files changed: 0 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/16651.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16651/head:pull/16651

PR: https://git.openjdk.org/jdk/pull/16651