Remove rest of time-trace message as it is inconsistent style

Other options which create output files don't produce output messages.
Improve documentation to help find trace file.

Differential Revision: https://reviews.llvm.org/D68710

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@374294 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed