[Reproducers] Copy over access/modification time in the FileCollector.
[Reproducers] Copy over access/modification time in the FileCollector.

Copy over access and modification time for the files included in the
reproducer. This is needed to pass tests that check the integrity of
object files based on their time stamp.

git-svn-id: 4c4cc70b1ef44ba2b7963015e681894188cea27e@364457 91177308-0d34-0410-b5e6-96231b3b80d8
(cherry picked from commit c5e41504e79863dce949277578db0419bec63fbc)

apple/swift-lldb,apple/swift-lldb,apple/swift-lldb,apple/swift-lldb,apple/swift-lldb,apple/swift-lldb