<signal.h> shouldn't get you the contents of <errno.h>, and <fcntl.h>
shouldn't get you the contents of <unistd.h>.
Change-Id: I347499cd8671bfee98e6b8e875a97cab3a3655d3
Modern architectures only get the *at(2) system calls. For example,
aarch64 doesn't have open(2), and expects userspace to use openat(2)
instead.
Change-Id: I87b4ed79790cb8a80844f5544ac1a13fda26c7b5