RFR: 8292329: Enable CDS shared heap for zero builds [v3]

[Ioi Lam]

> ZERO uses UseSerialGC by default. When we dump the default CDS archive during the build process, it fails to dump the shared heap (which requires G1GC).
> 
> The fix is to force -XX:+UseG1GC when dumping the default CDS archive during the build process.
> 
> Speed up:
> 
> (Before)
> $ perf stat -r 40 ./images/jdk/bin/java -version
> 0.018080 +- 0.000388 seconds time elapsed ( +- 2.15% )
> 
> (After)
> $ perf stat -r 40 ./images/jdk/bin/java -version
> 0.011986 +- 0.000205 seconds time elapsed ( +- 1.71% )

Ioi Lam has updated the pull request incrementally with one additional commit since the last revision:

  @magicus comments

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/9984/files
  - new: https://git.openjdk.org/jdk/pull/9984/files/f57ba86b..0d066921

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=9984&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=9984&range=01-02

  Stats: 4 lines in 1 file changed: 2 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/9984.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9984/head:pull/9984

PR: https://git.openjdk.org/jdk/pull/9984