RUMM-1145 Carthage XCFrameworks support

[buranmert]

Problem

The main thing of carthage is building projects for every possible arch-platform so that they don't need to be rebuilt when the developer changes the target arch-platform.
It was achieving this by lipoing BuildProducts for different arch-platforms and giving one single .framework containing multiple slices.

This model stopped working as arm64-simulator arch-platform came along with Apple Silicon; it duplicated arm64-ios and lipo doesn't merge duplicate slices.

Apple's solution

Apple introduced XCFrameworks to solve this problem: this format can contain multiple .frameworks for different arch-platforms.

Example.xcframework:
- ios-arm64_armv7/Example.framework
- ios-arm64_i386_x86_64-simulator/Example.framework
- macos-arm64_x86_64/Example.framework
- tvos-arm64/Example.framework
- tvos-arm64_x86_64-simulator/Example.framework
Info.plist

Carthage's solution

carthage started supporting this new format starting from 0.37.
carthage also maintains backward compatibility by not breaking projects that are configured for .framework dependencies.
For some reason (this looks like a bug in carthage to me), dd-sdk-ios works only in this backward-compatibility mode although it is configured with .xcframework

Backward compatibility

If the target has FRAMEWORK_SEARCH_PATH set to Carthage/Build/, carthage assumes that it searches for Example.framework whereas there is Example.xcframework instead.
In that case, carthage extracts the content of Example.xcframework and inject its location as an extra FRAMEWORK_SEARCH_PATH to xcodebuild

guard let platformTripleOS = settings.platformTripleOS.value,
  let frameworkSearchPaths = settings.frameworkSearchPaths.value,
  frameworkSearchPaths.contains(where: isRelativeToBuildDirectory) else {
  // don't extract
  return
}
extractXCFramework()
//

Setting such a FRAMEWORK_SEARCH_PATH value triggers XCFramework extraction and compilation succeeds ✅

ℹ️ Note that this build setting is not supposed to be needed for compilation.
ℹ️ Based on my trials, always the second target fails at building for iphonesimulator

Build settings of Kronos

Kronos had VALID_ARCHS in its base xcconfig file and it was not updated after the introduction of arm64-simulator.
I fixed it with MobileNativeFoundation/Kronos#76
I also asked for a hotfix version and I'm waiting for a response.

If Kronos ships a hotfix...

We can update to this version and dd-sdk-ios can be used by Apple Silicon owner carthage users ✅
Sooner or later, we will need to support this arch-platform.

Review checklist

• If Kronos ships a hotfix, remove the content of Base.xcconfig
• Feature or bugfix MUST have appropriate tests (unit, integration)
• Make sure each commit and the PR mention the Issue number or JIRA reference

[buranmert]

there is still something that i don't understand:
Datadog target links against Kronos.xcframework (not Kronos.framework)
i don't understand why it still requires extractXCFrameworks
once there is Carthage/Build/Kronos.xcframework in place, it builds without problem from Xcode

[ncreated]

Looks good 👌. I'm assuming something extra would have to be done for the crash-reporting branch once it's merged, but that's another work. Let's ship this as a hotfix?

[ncreated]

Great to see it gone 💪

[buranmert]

for the records:
this PR is a workaround, carthage is supposed to succeed without FRAMEWORK_SEARCH_PATHS
we can revert this workaround once there is news from Carthage/Carthage#3145