macOS 10.15.4b1 (19E224g) is missing /usr/bin/xar

I have the same problem. In fact, when Xcode (11.3.1) builds application distributions, it uses this utility too. This results in pretty obscure build error messages, like this:

ipatool failed with an exception: #<CmdSpec::NonZeroExitException: $ /Applications/Xcode.11.3.1.app/Contents/Developer/usr/bin/bitcode-build-tool -v -t /Applications/Xcode.11.3.1.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin --sdk /Applications/Xcode.11.3.1.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS13.2.sdk -o /var/folders/gg/sn34249n0l53vhc0_36r3y3h0000gn/T/ipatool20200211-26412-6iu957/thinned-out/arm64/Payload/[APP.app]/Frameworks/libswiftCore.dylib --generate-dsym /var/folders/gg/sn34249n0l53vhc0_36r3y3h0000gn/T/ipatool20200211-26412-6iu957/thinned-out/arm64/Payload/[APP.app]/Frameworks/libswiftCore.dylib.dSYM --strip-swift-symbols /var/folders/gg/sn34249n0l53vhc0_36r3y3h0000gn/T/ipatool20200211-26412-6iu957/thinned-in/arm64/Payload/[APP.app]/Frameworks/libswiftCore.dylib
Status: pid 26742 exit 2
Stdout:
    Debug: SDK path: /Applications/Xcode.11.3.1.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS13.2.sdk
    Debug: SDK version: 13.2
    Debug: PATH: ['/Applications/Xcode.11.3.1.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin', '/Applications/Xcode.11.3.1.app/Contents/Developer/usr/bin']
    Debug: Using: /Applications/Xcode.11.3.1.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/lipo
    MachoInfo: cd /
    "/Applications/Xcode.11.3.1.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/lipo" "-info" "/var/folders/gg/sn34249n0l53vhc0_36r3y3h0000gn/T/ipatool20200211-26412-6iu957/thinned-in/arm64/Payload/[APP.app]/Frameworks/libswiftCore.dylib"
    -= Output =-
    Non-fat file: /var/folders/gg/sn34249n0l53vhc0_36r3y3h0000gn/T/ipatool20200211-26412-6iu957/thinned-in/arm64/Payload/[APP.app]/Frameworks/libswiftCore.dylib is architecture: arm64
    Exited with 0
    
    Debug: Command took 0 seconds
    Debug: Using: /Applications/Xcode.11.3.1.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/dwarfdump
    GetUUID: cd /
    "/Applications/Xcode.11.3.1.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/dwarfdump" "-u" "/var/folders/gg/sn34249n0l53vhc0_36r3y3h0000gn/T/ipatool20200211-26412-6iu957/thinned-in/arm64/Payload/[APP.app]/Frameworks/libswiftCore.dylib"
    -= Output =-
    UUID: AD0CAD3B-1B51-3327-8644-8BE1FF1F0AE9 (arm64) /var/folders/gg/sn34249n0l53vhc0_36r3y3h0000gn/T/ipatool20200211-26412-6iu957/thinned-in/arm64/Payload/[APP.app]/Frameworks/libswiftCore.dylib
    Exited with 0
    
    Debug: Command took 0 seconds
    Debug: Using: /Applications/Xcode.11.3.1.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/segedit
    ExtractXAR: cd /
    "/Applications/Xcode.11.3.1.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/segedit" "/var/folders/gg/sn34249n0l53vhc0_36r3y3h0000gn/T/ipatool20200211-26412-6iu957/thinned-in/arm64/Payload/[APP.app]/Frameworks/libswiftCore.dylib" "-extract" "__LLVM" "__bundle" "/var/folders/gg/sn34249n0l53vhc0_36r3y3h0000gn/T/libswiftCore.dylibsf1ejW/libswiftCore.dylib.arm64.xar"
    -= Output =-
    Exited with 0
    
    Debug: Command took 0 seconds


Stderr:
    bitcode-build-tool internal error
    Traceback (most recent call last):
      File "/Applications/Xcode.11.3.1.app/Contents/Developer/usr/bin/bitcode-build-tool", line 10, in <module>
        bitcode_build_tool_main(sys.argv)
      File "/Applications/Xcode.11.3.1.app/Contents/Developer/usr/bin/../lib/bitcode_build_tool/main.py", line 83, in main
        map(input_macho.buildBitcode, input_macho.getArchs())
      File "/Applications/Xcode.11.3.1.app/Contents/Developer/usr/bin/../lib/bitcode_build_tool/macho.py", line 130, in buildBitcode
        bitcode_bundle = BitcodeBundle(arch, bundle, output_path).run()
      File "/Applications/Xcode.11.3.1.app/Contents/Developer/usr/bin/../lib/bitcode_build_tool/bundle.py", line 67, in __init__
        super(BitcodeBundle, self).__init__(input_xar)
      File "/Applications/Xcode.11.3.1.app/Contents/Developer/usr/bin/../lib/bitcode_build_tool/bundle.py", line 26, in __init__
        out = subprocess.check_output(cmd)
      File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/subprocess.py", line 216, in check_output
        process = Popen(stdout=PIPE, *popenargs, **kwargs)
      File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/subprocess.py", line 394, in __init__
        errread, errwrite)
      File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/subprocess.py", line 1047, in _execute_child
        raise child_exception
    OSError: [Errno 2] No such file or directory


>
    /Applications/Xcode.11.3.1.app/Contents/Developer/usr/bin/ipatool:297:in `run'
    /Applications/Xcode.11.3.1.app/Contents/Developer/usr/bin/ipatool:2703:in `block in CompileOrStripBitcodeInBundle'
    /Applications/Xcode.11.3.1.app/Contents/Developer/usr/bin/ipatool:2642:in `each'
    /Applications/Xcode.11.3.1.app/Contents/Developer/usr/bin/ipatool:2642:in `CompileOrStripBitcodeInBundle'
    /Applications/Xcode.11.3.1.app/Contents/Developer/usr/bin/ipatool:2902:in `block in ProcessIPA'
    /Applications/Xcode.11.3.1.app/Contents/Developer/usr/bin/ipatool:2864:in `each'
    /Applications/Xcode.11.3.1.app/Contents/Developer/usr/bin/ipatool:2864:in `ProcessIPA'
    /Applications/Xcode.11.3.1.app/Contents/Developer/usr/bin/ipatool:3811:in `<main>'

Hope this will be fixed soon.

I managed to get this command line utility from previous version of macOS and alter Xcode build script to use that. Seems to work, but for release builds I will have to use 10.14.

I too observe this impacting us. Is there any response for FB7568175?

Is there any response for FB7568175?

Nope.

/usr/bin/xar is now available in the update:10.15.4 Beta (19E234g).

Confirmed & closed FB7568175.