On Windows, fs::rename() could fail is another process was reading the
file at the same time using fs::openFileForRead(). In most cases the user
wouldn't notice as fs::rename() will continue to retry for 2000ms. Typically
this is enough for the read to complete and a retry to succeed, but if the
disk is being it too hard then the response time might be longer than the
retry time and the rename would fail with a permission error.
Add FILE_SHARE_DELETE to the sharing flags for CreateFileW() in
fs::openFileForRead() and try ReplaceFileW() prior to MoveFileExW()
in fs::rename().
Based on an initial patch by Edd Dawson!
Differential Revision: http://reviews.llvm.org/D13647
llvm-svn: 250046
