Setup testing target dependencies for default runtimes

Summary: The default runtimes targets aren't getting their dependencies configured correctly which results in check-runtimes failing when built from a clean build.

Reviewers: phosek, compnerd

Reviewed By: phosek

Subscribers: mgorny, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D63107

llvm-svn: 363015