RFR: 8364372: [Leyden] Set UseAOTCodeLoadThread ergonomically

[Ashutosh Mehra]

Without this fix:

[assembly phase]
$ java -Xlog:jit+thread=debug -XX:AOTMode=create -XX:AOTCache=jbench.aot -XX:AOTConfiguration=jbench.aotconf -cp JavacBench.jar JavacBench 100
...
[0.317s][debug][jit,thread] Added initial compiler thread C1 AOT code caching CompilerThread
[0.317s][debug][jit,thread] Added initial compiler thread C2 AOT code caching CompilerThread
..

With this fix, these threads are only in the production phase, not in the assembly phase.

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Commit messages:
 - 8364372: [Leyden] Set UseAOTCodeLoadThread ergonomically

Changes: https://git.openjdk.org/leyden/pull/89/files
  Webrev: https://webrevs.openjdk.org/?repo=leyden&pr=89&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8364372
  Stats: 6 lines in 3 files changed: 1 ins; 3 del; 2 mod
  Patch: https://git.openjdk.org/leyden/pull/89.diff
  Fetch: git fetch https://git.openjdk.org/leyden.git pull/89/head:pull/89

PR: https://git.openjdk.org/leyden/pull/89