CentOS tests were blocked due to issue https://github.com/dotnet/corefx/issues/5066.
It has been fixed with the latest NetStandardLibrary, hence upgrading from 1.0.0-rc2-23616 to 1.0.0-rc2-23704.
With this fix the native shims are correctly restored by dnx for RID centos.7-x64.
Build becomes the new compile. It decides which project to compile and how. It checks for incremental preconditions
Compile's resonsibility is trimmed down to only knowing how to invoke the compiler on a project
