Summary:
Fixes https://bugs.llvm.org/show_bug.cgi?id=34922.
Apparently, the mode in **fdopen** gets simply ignored and Windows only cares about the mode of the original **open**.
I have verified this both with the simple case from bug 34922 and with a full Firefox build.
Reviewers: zturner
Reviewed By: zturner
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D38984
llvm-svn: 316048