runtime: ./build.sh -? is not helpful

./build.sh -?

There are new changes on how we build. Use this script only for generic
build instructions that apply for both build native and build managed.
Otherwise:

Before                Now
build.sh native      build-native.sh
build.sh managed     build-managed.sh

For more information: https://github.com/dotnet/corefx/blob/master/Documentation/project-docs/developer-guide.md
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Tools are already initialized
Error: Object reference not set to an instance of an object.    at Microsoft.DotNet.Execute.Setup.FormatSetting(String option, String value, String type, String toolName)
   at Microsoft.DotNet.Execute.Setup.BuildParametersForCommand(Dictionary`2 commandParameters, String toolName)
   at Microsoft.DotNet.Execute.Setup.BuildCommand(String commandSelectedByUser, List`1 parametersSelectedByUser, Dictionary`2 parameters)
   at Microsoft.DotNet.Execute.Setup.GetHelpCommand(String commandName, String alias)
   at Microsoft.Fx.CommandLine.CommandLineParser.GetHelp(Int32 maxLineWidth, String parameterSetName, Boolean displayGlobalQualifiers)
   at Microsoft.Fx.CommandLine.CommandLineParser.<>c.<ParseForConsoleApplication>b__0_0(CommandLineParser parser)
   at Microsoft.Fx.CommandLine.CommandLineParser.Parse(Action`1 parseBody, Action`1 helpHandler, Action`2 errorHandler, Setup setupContent, String[] args)
   at Microsoft.Fx.CommandLine.CommandLineParser.ParseForConsoleApplication(Action`1 parseBody, String[] args, Setup setupContent)
   at Microsoft.DotNet.Execute.Executor.DefineParameters(String[] args, Setup setupInformation)