debug: Fix clang open fortify wrapper (BZ 31927)

The clang open fortify wrapper from 4228baef added
a restriction where open with 3 arguments where flags do not
contain O_CREAT or O_TMPFILE are handled as invalid.  They are
not invalid, since the third argument is ignored, and the gcc
wrapper also allows it.

Checked x86_64-linux-gnu and with a yocto build for some affected
packages.
Tested-by: “Khem Raj <raj.khen@gmail.com&gt;”>