What we ended up with, run a small custom script - https://gist.github.com/alexcohn/53fb9e93699080f158b5721888edd578 as a pre-compile build step for each target that depends on the xcframework. The naïve approach is to check that the directory exists. It could be improved by triggering a build of the default target of the project that produces the xcframework, and proceeding to the script if that build is not nop.

I am not sure I understand your use case, but for me, I simply need a way to inject a custom header into requests that are handled by a WKWebView. With NSSelectorFromString(@"registerSchemeForCustomProtocol:"), I can do that for all WebViews in my app, but it would be OK to have to set this interceptor for https scheme for each WebView separately. I really hate the idea of having to modify the HTML content of each WebView with some javascript only to replace the https scheme with some custom scheme (then, I can use the documented setURLSchemeHandler as @eskimo demonstrates in another thread). Any hints?

Did you specify inputPaths and outputPaths for your scripts?

Yes, you can change IDEBuildOperationMaxNumberOfConcurrentCompileTasks by setting defaults write com.apple.dt.Xcode IDEBuildOperationMaxNumberOfConcurrentCompileTasks 14 or whatever, and this will effect all Xcode builds that start after that. Also, this will effect the command-line xcodebuild (but there, you can control it for each build with -jobs argument).