[code-reflection] RFR: add a pure java (no maven) build option

[Gary Frost]

Added  pure java builder (replacing `mvn clean compile jar:jar install`)

So after adding ~babylon/build/xxx-yyy-server-release/jdk/bin to your path (and setting JAVA_HOME accordingly) with env.bash 

You should be able to build hat + backends + examples with just 

./bld

  
Relies on hashbang via `#!/usr/bin/env java --enable-preview --source 24`  to launch the file using babylon jdk

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Commit messages:
 - add a pure java (no maven) build option
 - add a pure java (no maven) build option

Changes: https://git.openjdk.org/babylon/pull/245/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=245&range=00
  Stats: 265 lines in 3 files changed: 261 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/babylon/pull/245.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/245/head:pull/245

PR: https://git.openjdk.org/babylon/pull/245