[llvm/runtimes] Add runtimes as a dependency of clang-bootstrap-deps

Summary: With the new LLVM_ENABLE_RUNTIMES option introduced in https://reviews.llvm.org/D40233, compiler-rt can now be included as a runtime. Since compiler-rt is needed for PGO, runtimes needs to be included as a dependency of clang-bootstrap-deps when building the stage1 compiler.

Reviewers: beanz, phosek, compnerd, smeenai, plotfi, xiaobai

Reviewed By: phosek

Subscribers: smeenai, beanz, phosek, mgorny, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D71430