[code-reflection] Integrated: bld script and bldr tools cleanup

[Gary Frost]

Some `bld` script maintenance and some `bldr/../Bldr.java` features to allow `jextract` and `java` execution from scripts

Added more checks to `hatrun.bash`

Added java launcher version of `hatrun.bash` called `hatrun` (chmod +x)

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Commit messages:
 - bld script and bldr tools cleanup
 - bld script and bldr tools cleanup

Changes: https://git.openjdk.org/babylon/pull/266/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=266&range=00
  Stats: 911 lines in 6 files changed: 664 ins; 136 del; 111 mod
  Patch: https://git.openjdk.org/babylon/pull/266.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/266/head:pull/266

PR: https://git.openjdk.org/babylon/pull/266