RFR: 8290981: Enable CDS for zero builds

[Ioi Lam]

Enable CDS for zero builds. `java --version` is about 2x faster now.


$ perf stat -r 40 ./images/jdk/bin/java -Xshare:off -version
0.034645 +- 0.000044 seconds time elapsed  ( +-  0.13% )
$ perf stat -r 40 ./images/jdk/bin/java -version
0.018080 +- 0.000388 seconds time elapsed  ( +-  2.15% )

I also fixed a bug in Images.gmk that always wrote the default archive to $JAVA_HOME/lib/server. This fix also makes it possible for a client libjvm to have a default CDS archive.

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Commit messages:
 - clean up C code
 - 8290981: Enable CDS for zero builds

Changes: https://git.openjdk.org/jdk/pull/9869/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9869&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8290981
  Stats: 85 lines in 5 files changed: 32 ins; 25 del; 28 mod
  Patch: https://git.openjdk.org/jdk/pull/9869.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9869/head:pull/9869

PR: https://git.openjdk.org/jdk/pull/9869