fix: do not use variable out of its scope

[mdelapenya]

What does this PR do?

It avoids using the platform variable out of its Groovy scope.

Why is it important?

The pipeline will fail whenever the else branch of the isGitRegionMatch is false. This bug will appear whenever there is a replay in the pipeline, or there are no changes in the git-regions defined by the regex. Before these changes, the log entry in the else branch would try to print the platform, which was declared in the if branch of the evaluation.

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have run the Unit tests (make unit-test), and they are passing locally
• I have run the End-2-End tests for the suite I'm working on, and they are passing locally
• I have noticed new Go dependencies (run make notice in the proper directory)

Related issues

• Caused by feat: add support for running the tests in ARM #707

Follows-up

Backport to 7.x and 7.13.x

[elasticmachine]

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Build stats

• Build Cause: Pull request #1231 opened

• Start Time: 2021-06-02T06:04:02.929+0000

• Duration: 26 min 57 sec

• Commit: 495c802

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Test	Results
Failed	0
Passed	202
Skipped	0
Total	202

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Test stats 🧪

Test	Results
Failed	0
Passed	202
Skipped	0
Total	202