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: I6b2a3694f85565afdeb782585c6af36e8c4d1557
1 file changed