ObjC->Swift plugin migration caused a size regression in the gallery app because the Swift runtime was also pulled in.  

The gallery app minimum target version is iOS 11.0, which predates Swift ABI compatibility.  Pre iOS 12.2 apps embedded the Swift runtime since there wasn't one available to use in the OS.  

Add  `FLUTTER_XCODE_IPHONEOS_DEPLOYMENT_TARGET` to the compile perf test environment, which gets translated by the tool to an Xcode build setting:
```
[2023-12-14 15:52:14.797318] [STDOUT] stdout:                IPHONEOS_DEPLOYMENT_TARGET = 12.2
```

On my machine on main
```
    "release_size_bytes": 43717389,
```
becomes
```
    "release_size_bytes": 40679432,
```

Fixes https://github.com/flutter/flutter/issues/139605