Prefer StringBuilder for local variables #502

Job	Run time
Verify / setup-maven-version	0s
Verify / ${{ inputs.ff-os }} jdk-${{ inputs.ff-jdk }}-${{ inputs.ff-jdk-distribution }} ${{ needs.setup-maven-version.outputs.version }}	0s
Verify / ${{ matrix.os }} jdk-${{ matrix.jdk }}-${{ matrix.distribution }} ${{ matrix.maven }}	0s
	0s

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