Update build.sh

[Pterjudin]

This PR refactors the Terraform build script to improve maintainability, readability, and error handling. Key changes include:

• Replacing redundant code blocks with reusable functions for consistency and simplicity.
• Adding robust error handling to prevent unintended behavior, such as halting execution on directory navigation failure.
• Enhancing portability by replacing which with command -v for environment checks.
• Organizing the script into logical sections with clear comments, improving readability for future maintainers.
• Ensuring directories like GOPATH/bin are created dynamically, avoiding runtime errors.
• Streamlining the packaging process with recursive zipping for all platform builds.

These changes enhance the developer experience, ensure a consistent build process, and reduce the risk of errors during multi-platform builds.

Target Release

1.11.x

Draft CHANGELOG entry

ENHANCEMENTS

• Refactored the Terraform build script for improved readability, maintainability, and error handling.
• Enhanced portability by replacing which with command -v for environment checks.
• Improved error handling for directory navigation and missing directories during builds.
• Streamlined the multi-platform packaging process with recursive zipping of build outputs.

[hashicorp-cla-app]

All committers have signed the CLA.

[crw]

Hi @Pterjudin, to set expectations, we do not normally accept outside contributions to build scripts. Can you say something about what motivated this change?