Support using Auth0 as a submodule, without Carthage/Swift Package Manager

[hoolrory]

Checklist

• I have looked into the Readme, Examples, and FAQ and have not found a suitable solution or answer.
• I have looked into the API documentation and have not found a suitable solution or answer.
• I have searched the issues and have not found a suitable solution or answer.
• I have searched the Auth0 Community forums and have not found a suitable solution or answer.
• I agree to the terms within the Auth0 Code of Conduct.

Describe the problem you'd like to have solved

We have added Auth0.swift, JWTDecode.swift, and SimpleKeychain as submodules to our project. However since the Auth0 framework does not explicitly link JWTDecode.swift and SimpleKeychain build errors result on clean builds, as Auth0 may attempt to build before JWTDecode.swift and SimpleKeychain have.

Describe the ideal solution

We have forked Auth0 and made these dependencies explicit in Auth0 framework targets, by adding both JWTDecode and SimpleKeychain to "Link Binary With Libraries":

This makes the dependency explicit, and ensures that JWTDecode and SimpleKeychain are built before Auth0.

Alternatives and current workarounds

We attempted to resolve this by simply moving JWTDecode to higher in our dependency list, but because Xcode builds things in parallel this wasn't enough to make sure JWTDecode was built before Auth0.

Additional context

No response