Fix watchOS preview build issue

[sergeirr]

For some reason Xcode watchOS SwiftUI preview attempts to build this package against watchOS SDK.
Fixed by adding os type check.
Tested with:

• iOS Preview
• watchOS Preview
• iOS build
• watchOS build

Fixes #111

[sergeirr]

Additional description: https://developer.apple.com/forums/thread/731732

[davdroman]

Thanks for your PR.

Is there any way we could add a CI check to make sure this doesn't break with future iterations?

[sergeirr]

I'm not sure about this. I don't know if it is possible to "Build to Preview" from the command line to reproduce the problem.

[davdroman]

Okay I'll look into this. I wouldn't want to merge without some assurance from CI. I'll try my best to get it sorted asap.

[sergeirr]

I see.
Another workaround for developers is to temporary remove the iOS main app target from the watchOS scheme when you want to work with watchOS SwiftUI Previews.

[sergeirr]

@davdroman You can mention me if you need some help with an example project to reproduce this.

[davdroman]

@sergeirr yes please, I'd certainly appreciate an example project.

[sergeirr]

@davdroman This is the project https://github.com/sergeirr/WatchOSIntrospect
There are 2 branches (excluding main):

1. With issue (added origin SwiftUIIntrospect package)
2. Without issue (added forked by me SwiftUIIntrospect package)

[davdroman]

Thanks! This is very helpful to get going.