[FIX] Add iOS sourcemap file export when sentry is enabled

[marco-saia-datadog]

What does this PR do?

Clone of #75 by @sidorchukandrew.

This PR adds exporting the sourcemap file location to the if branch where Sentry is present in the build phase. When Sentry isn't present, it already adds this env variable export. This PR brings the Sentry case into alignment with when Sentry is not present

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests
• Make sure you discussed the feature or bugfix with the maintaining team in an Issue
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• If this PR is auto-generated, please make sure also to manually update the code related to the change