To Reproduce:

1. Build empty app with 5.6 & 5.4.
2. Archive it in Xcode
3. Observe:
- app without binary 5.2mb vs 5.1 vs 4.9 (5.6 vs 5.5 vs 5.4)
- bin all relevant segments (TEXT & DATA) are ~2.5% larger on 5.6. (See linked spreadsheet)

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RESOLUTION
It looks like that there's no single place where code size has increased a lot. The size of code in Unity just increased a little bit everywhere. This means that it's not possible to fix this particular regression. However, we will still look into how to reduce application size in other areas.