Errors and Warnings after upgrading all Xamarin components today

I'm getting 100 warnings much like this one:
Warning 87 The element 'Target' in namespace 'http://schemas.microsoft.com/developer/msbuild/2003' has invalid child element 'Ditto' in namespace 'http://schemas.microsoft.com/developer/msbuild/2003'. List of possible elements expected: 'Task, AL, AspNetCompiler, AssignCulture, AssignProjectConfiguration, AssignTargetPath, AxImp, CallTarget, CombinePath, ConvertToAbsolutePath, Copy, CreateCSharpManifestResourceName, CreateItem, CreateProperty, CreateVisualBasicManifestResourceName, Csc, Delete, Error, Exec, FindAppConfigFile, FindInList, FindUnderPath, FormatUrl, FormatVersion, GenerateApplicationManifest, GenerateBootstrapper, GenerateDeploymentManifest, GenerateResource, GenerateTrustInfo, GetAssemblyIdentity, GetFrameworkPath, GetFrameworkSdkPath, GetReferenceAssemblyPaths, LC, MakeDir, Message, Move, MSBuild, ReadLinesFromFile, RegisterAssembly, RemoveDir, RemoveDuplicates, RequiresFramework35SP1Assembly, ResolveAssemblyReference, ResolveComReference, ResolveKeySource, ResolveManifestFiles, ResolveNativeReference, ResolveNonMSBuildProjectOutput, SGen, SignFile, TlbImp, Touch, UnregisterAssembly, UpdateManifest, Vbc, VCBuild, Warning, WriteCodeFragment, WriteLinesToFile, XslTransformation, CodeAnalysis, CL, Link, BSCMake, CPPClean, Get.... C:\Program Files (x86)\MSBuild\Xamarin\iOS\Xamarin.iOS.Common.targets 1162 4 Miscellaneous Files