Xcode warnings after installing .pkg toolchains

After installing these toolchains Xcode shows warnings about missing `Info.plist` in all projects that it builds:

```
/Users/maxd/Library/Developer/Toolchains/swift-wasm-5.3-SNAPSHOT-2020-10-21-a.xctoolchain:1:1: 
failed to load toolchain: could not find Info.plist in /Users/maxd/Library/Developer/Toolchains/swift-wasm-5.3-SNAPSHOT-2020-10-21-a.xctoolchain
```
