TinyConstraints cannot run in x86_64 simulator on Xcode 12/13 due to VALID_ARCHS built setting

[eliburke]

e.g. Source.swift:9:8: Could not find module 'TinyConstraints' for target 'arm64-apple-ios-simulator'; found: i386, x86_64-apple-ios-simulator, x86_64, i386-apple-ios-simulator, at: ~Library/Developer/Xcode/DerivedData/APP_BUILD_DIR/Build/Products/Debug-iphonesimulator/TinyConstraints.framework/Modules/TinyConstraints.swiftmodule

The solution is to remove VALID_ARCHS, which has been deprecated.

https://developer.apple.com/documentation/xcode-release-notes/xcode-12-release-notes

The Build Settings editor no longer includes the Valid Architectures build setting (VALID_ARCHS), and its use is discouraged. Instead, there is a new Excluded Architectures build setting (EXCLUDED_ARCHS). If a project includes VALID_ARCHS, the setting is displayed in the User-Defined section of the Build Settings editor. (15145028)

Patch in #101

You may also want to remove your custom ENABLE_BITCODE setting, in case it breaks something down the road.