iOS/macOS app distribution failed while using framework after upgrading Xcode12 and macOS BigSur

We are unable to distribute our sample app which uses our framework as well as our users can't. While archiving and distributing to AppStore, the app is rejected with the following message:

Invalid Bundle - One or more dynamic libraries that are referenced by your app are not present in the dylib search path. If your app contains bitcode, bitcode processing may have failed. Because of these errors, this build of your app will not be able to be submitted for review or placed on the App Store.

The framework contain the bitcode, or at least there's a BITCODE_GENERATION_MODE = bitcode build setting in our .xcconfig, which basically means, the Xcode will add -fembed-bitcode build flag to any clang invocation.

From here, we've started testing using Ad-Hoc builds, to speed up our trial and error attempts, which also fails while Rebuild from bitcode option is selected. Organiser shows the popup with the following contents:

ipatool failed with an exception: #<CmdSpec::NonZeroExitException: $ /Applications/Xcode.app/Contents/Developer/usr/bin/python3 /Applications/Xcode.app/Contents/Developer/usr/bin/bitcode-build-tool -v -t /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin --sdk /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS14.2.sdk -o /var/folders/vz/b0jj0dms4014y5htfv93svfc0000gn/T/ipatool20201130-52097-13rj9hy/thinned-out/arm64/Payload/iosTest.app/Frameworks/SciChart.framework/SciChart --generate-dsym /var/folders/vz/b0jj0dms4014y5htfv93svfc0000gn/T/ipatool20201130-52097-13rj9hy/thinned-out/arm64/Payload/iosTest.app/Frameworks/SciChart.framework/SciChart.dSYM --strip-swift-symbols /var/folders/vz/b0jj0dms4014y5htfv93svfc0000gn/T/ipatool20201130-52097-13rj9hy/thinned-in/arm64/Payload/iosTest.app/Frameworks/SciChart.framework/SciChart
Status: pid 52150 exit 1
Stdout:
    SDK path: /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/

Logs provided isn't very informative, here is the snippet from IDEDistributionPipeline.log

    -= Output =-
    ld: warning: -sdk_version and -platform_version are not compatible, ignoring -sdk_version
    Undefined symbols for architecture arm64:
      "___llvm_profile_runtime", referenced from:
          __hidden#25821_ in 0832.o
          __hidden#25821_ in 0833.o
          __hidden#25821_ in 0834.o
          __hidden#25821_ in 0835.o
          __hid
2020-11-30 16:19:17 +0000  den#25821_ in 0836.o
          __hidden#25821_ in 0837.o
          __hidden#25821_ in 0838.o
          ...
    ld: symbol(s) not found for architecture arm64
    Exited with 1z
    
    Failed to compile bundle: /var/folders/vz/b0jj0dms4014y5htfv93svfc0000gn/T/SciChart6aun_sfs/SciChart.arm64.xar

Stderr:

    from /Applications/Xcode.app/Contents/Developer/usr/bin/ipatool:2808:in `block in CompileOrStripBitcodeInBundle'
    from /Applications/Xcode.app/Contents/Developer/usr/bin/ipatool:2747:in `each'
    from /Applications/Xcode.app/Contents/Developer/usr/bin/ipatool:2747:in `CompileOrStripBitcodeInBundle'
    from /Applications/Xcode.app/Contents/Developer/usr/bin/ipatool:3016:in `block in ProcessIPA'
    from /Applications/Xcode.app/Contents/Developer/usr/bin/ipatool:2978:in `each'
    from /Applications/Xcode.app/Contents/Developer/usr/bin/ipatool:2978:in `ProcessIPA'
    from /Applications/Xcode.app/Contents/Developer/usr/bin/ipatool:3928:in `<main>'
2020-11-30 16:19:17 +0000  /Applications/Xcode.app/Contents/Developer/usr/bin/ipatool exited with 1

which after bunch of warnings shows the actual error at the end of file (I can't include full log, since it's too much of a raw text):

            code = 1061;
            description = "ipatool failed with an exception: #<CmdSpec::NonZeroExitException: ...
            info =             {
            };
            level = ERROR;
            type = exception;

Not sure what to to do with this, I've tried different build settings options, nothing helped... Already contacted apple, but no feedback yet, and knowing them, we can wait far too long...

The strange part here, is if we include our .framework directly as a source code and then archive the app - everything works as expected. If we include it as XCFramework or just .framework, which is pre-built - it fails as described above.

I might miss something simple or obvious here, so please let me know if somebody have some insights on that matter.

Some system info:
macOS BigSur 11.0.1
XCode Version 12.2 (12B45b)

We've tried different combinations of macOS and Xcode, e.g.:

Catalina with Xcode 12
BigSur with Xcode 11
etc.

Any help is greatly appreciated. Thanks.

Long story short, there were LLVM instrumentation included, which prevents AppStore processing. I've written a whole blog post about it here - https://blog.scichart.com/xcframework-xcode-12-and-bigsur-issues/

To sum up, here is a few required steps to make sure while creating XCFramework for distribution:

• Using archive builds is a MUST, release build isn't enough
• BUILD_LIBRARY_FOR_DISTRIBUTION must be set to YES
• SKIP_INSTALL must be set to NO
• GCC_INSTRUMENT_PROGRAM_FLOW_ARCS = NO to turn off GCC instrumentation and remove them from the binary
• CLANG_ENABLE_CODE_COVERAGE = NO to turn off code coverage tools from the binary

Having all of the above helped to solve our preparing and distribution problem and hopefully save you some time if you happened to face same issues as we did.