Fixes #26930: Fix false positive in prerequisite check

[oluies]

Here is the completed PR description based on the fix we discussed. You can copy and paste this directly into your GitHub PR:

Describe your changes:

Fixes #26930

The check_prerequisites.sh script had a logic flaw where it used command substitution $(...) to call the check_command_existence function. In Bash, this spawns a subshell, meaning any updates to the global code variable (used to track failures) were lost once the subshell terminated. Consequently, the script would print errors for missing tools but still conclude with "✓ All prerequisites are met" and exit with a success code (0).

Changes made:

• Refactored the main loop to call functions directly instead of using subshells, allowing the code variable to persist.
• Updated check_version to use local variables correctly, preventing logic errors during version comparison.
• Replaced the which command with the more portable command -v.
• Fixed garbled character encoding for the terminal checkmarks/crosses.

How I tested these changes:

• Purposely uninstalled java and antlr4 and ran ./scripts/check_prerequisites.sh.
• Confirmed the script now correctly outputs ✗ ERROR: Some prerequisites are not met. at the end.
• Verified the exit code is now 1 (or 2) instead of 0 when dependencies are missing.

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Type of change:

• Bug fix
• Improvement
• New feature
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation

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Checklist:

• I have read the [CONTRIBUTING](https://docs.open-metadata.org/developers/contribute) document.

• My PR title is Fixes #<ISSUE_NUMBER>: Fix false positive in prerequisite check

• I have commented on my code, particularly in hard-to-understand areas.

• I have verified the fix by running the script in an environment with missing dependencies.

[github-actions]

Hi there 👋 Thanks for your contribution!

The OpenMetadata team will review the PR shortly! Once it has been labeled as safe to test, the CI workflows
will start executing and we'll be able to make sure everything is working as expected.

Let us know if you need any help!

[github-actions]

Hi there 👋 Thanks for your contribution!

The OpenMetadata team will review the PR shortly! Once it has been labeled as safe to test, the CI workflows
will start executing and we'll be able to make sure everything is working as expected.

Let us know if you need any help!

[gitar-bot]

Code Review ✅ Approved

Fixes false positive in prerequisite check that was incorrectly reporting all prerequisites as met. No issues found.

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