RFR: 8365512: Replace -Xcomp with -Xmixed for AOT assembly phase [v2]

[Vladimir Kozlov]

> When debugging AOT code generation in Leyden repo I noticed that AOT JIT compilations are serial with -Xcomp even so we create a lot of compiler threads to speed up. It is because -Xcomp enforce blocking compilation and only one thread submits AOT compilations. Also -Xcomp triggers a lot more other, not AOT, compilations which we don't need during assembly phase.
> 
> I suggest to replace -Xcomp with -Xmixed for AOT assembly phase.
> 
> I want to push it into mainline first because in mainline we don't even do AOT compilation yet.
> 
> This should speed up AOT testing with -Xcomp.
> 
> Tested tier1-6,8,10 (-rt)

Vladimir Kozlov has updated the pull request incrementally with one additional commit since the last revision:

  Update comment

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Changes:
  - all: https://git.openjdk.org/jdk/pull/26767/files
  - new: https://git.openjdk.org/jdk/pull/26767/files/08bd075f..60861d3a

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=26767&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=26767&range=00-01

  Stats: 5 lines in 1 file changed: 2 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/26767.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26767/head:pull/26767

PR: https://git.openjdk.org/jdk/pull/26767