Add a setLastModificationAndAccessTime to PathV2.

With this we can remove the last use of PathV1 from llvm-ar.cpp.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@184464 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Support/FileSystem.h

@@ -482,6 +482,8 @@ error_code status(const Twine &path, file_status &result);
 ///          platform specific error_code.
 error_code permissions(const Twine &path, perms prms);
 
+error_code setLastModificationAndAccessTime(int FD, TimeValue Time);
+
 /// @brief Is status available?
 ///
 /// @param s Input file status.