Add mode to open call with O_CREAT

This change was already applied internally. For us to submit FORTIFY, we
need to push it out here. Otherwise, we get compile-time errors about
this.

Bug: 32073964
Test: Builds with FORTIFY.
Change-Id: Ib500aca933468c06f7ceb796a9bb6a16c118e366
Merged-In: I63eb3d5499ae7e9ff9a77393763e39b747fd4611