Support, LTO: When pruning a directory, ignore files matching a prefix.

This is a safeguard against data loss if the user specifies a directory
that is not a cache directory. Teach the existing cache pruning clients
to create files with appropriate names.

Differential Revision: https://reviews.llvm.org/D31109

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@298271 91177308-0d34-0410-b5e6-96231b3b80d8
5 files changed