Improved build script

[criadoperez]

Makes 2 improvements:

1. Checks if git is installed before executing the command. If not, it will inform the user to do so.
2. Git Tag Check: The command git tag --points-at HEAD might produce multiple tags. To handle this scenario, it will use the first one if it happens.

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[ekpyron]

Thanks for the PR, but we don't see a particular need for these changes and checking for the first git tag is not necessarily correct if there were more tags either, so we're closing the PR.