fix: Benchmark Upload

[maxep]

What and why?

Set env DD_BENCHMARK for benchmark build

Review checklist

• [ ] Feature or bugfix MUST have appropriate tests (unit, integration)
• [ ] Make sure each commit and the PR mention the Issue number or JIRA reference
• [ ] Add CHANGELOG entry for user facing changes

[datadog-datadog-prod-us1[bot]]

Datadog Report

Branch report: maxep/fix/benchmark-upload Commit report: 0b8f312 Test service: dd-sdk-ios

:white_check_mark: 0 Failed, 1866 Passed, 0 Skipped, 1m 17.09s Total Time :small_red_triangle_down: Test Sessions change in coverage: 4 decreased, 1 increased (+0.02%), 3 no change

:small_red_triangle_down: Code Coverage Decreases vs Default Branch (4)

• test DatadogRUMTests iOS 81.74% (-0.05%) - Details
• test DatadogInternalTests iOS 79.63% (-0.02%) - Details
• test DatadogTraceTests iOS 54.34% (-0.02%) - Details
• test DatadogSessionReplayTests iOS 30.49% (-0.02%) - Details