Add permission bits to open with O_CREAT.

It's an error to pass open O_CREAT without giving it mode bits:
https://linux.die.net/man/3/open

Bug: 32073964
Test: Compiles with clang FORTIFY.
Change-Id: Iaa78c3003ed960e1ffe7e56623dba33db4e17443
1 file changed