RFR: 8288282: Zero-release build is broken after JDK-8279047 due to UseHeavyMonitors is read-only

[Jie Fu]

Hi all,

Zero-release build is broken after JDK-8279047.
After JDK-8279047, `UseHeavyMonitors` becomes read-only in PRODUCT VMs.

But for Zero, `UseHeavyMonitors` needs to be reset if `DiagnoseSyncOnValueBasedClasses != 0`.

  // If lock diagnostics is needed, always call to runtime
  if (DiagnoseSyncOnValueBasedClasses != 0) {
    FLAG_SET_DEFAULT(UseHeavyMonitors, true);
  }


I never hear that people would DiagnoseSyncOnValueBasedClasses with zero vms.
So in order to expire `UseHeavyMonitors` for all PRODUCT VMs, I suggest disabling lock diagnostics for zero vms.

Thanks.
Best regards,
Jie

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

Commit messages:
 - 8288282: Zero-release build is broken after JDK-8279047 due to UseHeavyMonitors is read-only

Changes: https://git.openjdk.org/jdk/pull/9138/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=9138&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8288282
  Stats: 4 lines in 1 file changed: 1 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/9138.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9138/head:pull/9138

PR: https://git.openjdk.org/jdk/pull/9138