Xcode 11.4 : Building for iOS Simulator but the linked library was built for Mac OS + iOS

@robby28: Bosian's solution worked for me. My code also needed to only include references to the framework when not building for simulator, like so:

#if ! TARGET_IPHONE_SIMULATOR
#import <myDeviceOnlyFramework>
#endif

That should prevent linking failure errors.

I totally support you! Not even a note in the Release Notes of Xcode 11.4. I'm struggling with a similar problem for days now and the only thing that I have to support my need for recompilation of a third-party lib is a forum's answer. That's not good. This kind of disruption is not helpful for anyone.

@ccmargo - totally concur. Its beyond me why this is now a critical error.
I cant even strip a universal library down to its x86_64 arch in a script file phase, it errors prior to hitting the script. This is a huge disruption to developers who rely on 3rd party tooling.
Why does Apple constantly have to re-invent the wheel?

We encountered the same problem. This is what I found out:

When a static library is added to the Xcode project (through Build Phases -> Link Binary With Libraries -> Add Other), Xcode automatically adds the relative path to that .a file to its file reference entry.

Prior to Xcode 11.4, this path was apparently removed during build, and replaced by the evaluated path generated from the current build settings, i.e. the actual configuration (Debug/Release) and the actual platform (iphoneos or iphonesimulator).

Starting from Xcode 11.4 however, this is apparently not happening anymore, and the build system is always using the explicit path set when the library was added.

By manually editing the project.pbxproj file for the iOS project, I removed the "path" attribute from the respective entries, e.g. changed from

  A15F487B16C934CE00D6F824 /* libmurl_engine.a */ = {
    isa = PBXFileReference;
    lastKnownFileType = archive.ar;
    name = libmurl_engine.a;
    path = "ios/Release-iphoneos/libmurl_engine.a";
    sourceTree = "";
  };

to

  A15F487B16C934CE00D6F824 /* libmurl_engine.a */ = {
    isa = PBXFileReference;
    lastKnownFileType = archive.ar;
    name = libmurl_engine.a;
    sourceTree = "";
  };

After this change, I was able to compile the project for both the actual iOS target as well as the simulator.

Hope that helps.