[code-reflection] Integrated: Updated babylon and hat build docs

[Gary Frost]

Updated markdown docs for building babylon and hat

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Commit messages:
 - Updated babylon and hat build docs

Changes: https://git.openjdk.org/babylon/pull/233/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=233&range=00
  Stats: 361 lines in 14 files changed: 195 ins; 138 del; 28 mod
  Patch: https://git.openjdk.org/babylon/pull/233.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/233/head:pull/233

PR: https://git.openjdk.org/babylon/pull/233