RFR: Workaround CacheDataStore use with source launcher [v2]

[Aleksey Shipilev]

> I was trying to test the simplest workload that involves javac, and that is source launcher. When I attempt to use source launcher with `-XX:CacheDataStore`, it fails with:
> 
> 
> $ rm -f app.cds*; build/linux-x86_64-server-release/images/jdk/bin/java -XX:CacheDataStore=app.cds -Xmx256m -Xms256m -XX:+UnlockExperimentalVMOptions -XX:+UseEpsilonGC HelloStream.java
> [0.001s][warning][cds] optimized module handling/full module graph: disabled due to incompatible property: jdk.module.addmods=ALL-DEFAULT
> Error occurred during initialization of VM
> CacheDataStore cannot be created because AOTClassLinking is enabled but full module graph is disabled
> 
> 
> Source launcher adds `--add-modules=ALL-DEFAULT`:
> 
> 
> $ man java
> ...
>        In source-file mode, execution proceeds as follows:
> 
> ...
>        • The compiled classes are executed in  the  context  of  an  unnamed  module,  as  though  --add-mod‐
>          ules=ALL-DEFAULT  is  in  effect.  This is in addition to any other --add-module options that may be
>          have been specified on the command line.
> 
> 
> I think we can work that around specifically for Leyden, and also leave a TODO breadcrumb in the code that we need to figure this out on CDS side. This PR does that workaround. With it, source launcher works with simple examples:
> 
> 
> $ build/linux-x86_64-server-release/images/jdk/bin/java -XX:CacheDataStore=app.cds -Xmx256m -Xms256m -XX:+UnlockExperimentalVMOptions -XX:+UseEpsilonGC  HelloStream.java
> Warning: CacheDataStore cannot be used with default source launcher environment, disabling --add-modules=ALL-DEFAULT
> hello, world

Aleksey Shipilev has updated the pull request incrementally with one additional commit since the last revision:

  Indenting

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Changes:
  - all: https://git.openjdk.org/leyden/pull/15/files
  - new: https://git.openjdk.org/leyden/pull/15/files/5c198f7d..4e490f86

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=leyden&pr=15&range=01
 - incr: https://webrevs.openjdk.org/?repo=leyden&pr=15&range=00-01

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/leyden/pull/15.diff
  Fetch: git fetch https://git.openjdk.org/leyden.git pull/15/head:pull/15

PR: https://git.openjdk.org/leyden/pull/15