Add a frontend option -chained-pch and don't pass an active PCH reader to the PCH writer if it is not set, preventing creation of chained PCH files. Since the reader is so far unused, effectively no functionality change.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@107936 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed